There are a lot of reasons to love the AR-15 platform. It’s easy to shoot, cost-effective, and powerful. It’s also extremely modular, allowing you to add or remove accessories in the hopes of creating a weapon with a distinct flavor or optimized for a specific use.
For the uninitiated, however, having infinite options can be overwhelming. And, without a robust knowledge of materials, finishes, and specifications, it’s impossible to effectively compare one AR-15 with another.
But you don’t need to be an engineer to grasp these concepts. If you know what your basic requirements are then finding the right AR-15 should be straightforward once you’ve gained a bit of knowledge. And, this guide will cover the aforementioned topics, thoroughly.
Before you get bogged down by the details, I want to give you a good idea of what’s available. I’ve listed eight options that represent the absolute best AR-15 rifles on the market based on objective facts and personal observation or observations of close friends and acquaintances. It’s certainly not scientific, so keep that in mind.
I also provide an in-depth review of all my top picks. That way you have a clear idea of what sets them apart from the competition and exactly why I picked them. If you want to expand your knowledge and really become an expert, stay tuned for the rest of the guide.
Top 8 Best AR-15 Rifles
Aero Precision AC-15
Aero Precision is quickly becoming my go-to for my AR-15 needs. Simply put, they offer an awesome product at a great price – their AC-15 is more of the same. MSRP for this rifle is $699 but you can find it for much less if you shop around.
Accuracy is very good with this AR-15 considering it has a drop-in handguard (non-free float) and a mil-spec trigger. I easily maintained sub 2″ groups at 100 yards with a scope.
Feature-wise, this is a typical mil-spec style weapon. It has an A2 flash hider, F-marked front sight post, polymer hand guard, mil-spec trigger, A2 pistol grip, and M4 collapsible buttstock.
The barrel itself is magnetic particle inspected, high-pressure tested and features a durable nitride finish inside and out. In addition, it’s made from mil-spec 4150 CMV steel, has a 1:7 twist rate, and extended feed ramps.
Both upper and lower receivers are made from high-quality 7075-T6 aluminum. The upper receiver is T-marked, which is a nice touch. And the lower receiver features a flared magazine well to allow for easier magazine changes. It also features a tension screw that guarantees a great fit between the upper and lower receivers.
The chrome-lined, full-auto bolt carrier is machined from 8620 steel and has a phosphate finish. The bolt is made from mil-spec Carpenter 158 steel and is high-pressure tested and magnetic particle inspected.
When you consider all of the features I mentioned and the awesome price, this is probably the best AR-15 available right now for the money.
See It HereBravo Company HSP The Jack Carbine
This AR-15 is built by Bravo Company in collaboration with Haley Strategic, two companies known for producing top-shelf equipment in their respective verticals. As far as off-the-shelf guns go, this is one of the best.
Design wise it’s obvious that this thing was built with reliability and performance in mind. It features a full complement of BCMGUNFIGHTER gear, to include the bolt carrier group, charging handle, pistol grip, and compensator.
It also comes with a Geissele SMR Mk1 handguard, ALG Defense ACT trigger, B5 Systems SOPMOD Bravo buttstock, and BCM branded Troy Industries backup iron sights. To round things out, it’s finished in Disruptive Grey Cerakote.
This model has a 14.5″ cold hammer forged, 4150 CMV steel, chrome lined barrel with a 1:7 twist rate. The permanently attached compensator, low profile gas block, and mid-length gas system make this thing a dream to shoot.
Everything is properly tested and inspected to guarantee reliability. Overall, this is a fantastic weapon and you’ll struggle to find any faults at all.
See It HereBravo Company RECCE-16 Carbine
Bravo Company manufactures some of the best AR-15 parts and accessories available. And that’s not just my opinion. Even a cursory search will reveal countless reviews attesting to their quality. Their RECCE-16 Carbine is certainly no different and worth every penny.
Accuracy with this weapon is phenomenal, sometimes achieving 1″ groups at 100 yards with magnification. The free float handguard and smooth PNT trigger really work wonders here.
The government profile barrel is made from mil-spec 4150 CMV steel that is phosphate finished, chrome lined, high-pressure tested, and magnetic particle inspected. It has a 1:7 twist rate and is topped off with Bravo Company’s MOD 0 hybrid compensator.
There are a number of handguard options available, though mine came with Bravo Company’s awesome KMR Alpha 13 rail. It’s extremely comfortable, lightweight, and with seven available mounting angles, it’s very practical. Of course, it has a Picatinny rail section on top to mount optics and other accessories.
Both upper and lower receivers are made from forged 7075-T6 aluminum and are available in a wide range of finishes. That includes hard-coat anodizing and Cerakote. The rifle also comes with Bravo Company’s very popular MOD 4 charging handle and extended trigger guard.
The chrome-lined, full-auto bolt carrier is machined from 8620 steel and has a phosphate finish. The bolt is made from mil-spec Carpenter 158 steel and is high-pressure tested and magnetic particle inspected.
To round things out, you also get Bravo Company’s Mod 3 pistol grip, quick disconnect end plate, and Mod 0 buttstock. This is certainly a lot of gun for the money. It is great for a wide range of uses including personal defense or even light competition.
See It HereColt LE6940
While it’s not much of a departure from other mil-spec looking rifles or even the cheaper LE6920 model, I think Colts LE6940 deserves a spot on the list.
Accuracy is very good with this gun and marginally better than the LE6920 due to it’s free-float, monolithic upper receiver design. The upper receiver and handguard are actually one solid piece – a feature meant to improve overall durability and accuracy.
The only other feature differentiating the LE6940 from the LE6920 is the proprietary folding front sight, which is actually very nice. Also included is a Magpul MBUS rear sight and 30 round Magpul PMAG.
The chrome lined, phosphate finished barrel is made from mil-spec 4150 CMV steel and has a 1:7 twist rate. Everything is high-pressure tested and magnetic particle inspected.
Both the monolithic upper receiver and lower receiver are made from forged 7075-T6 aluminum. The chrome-lined, full-auto bolt carrier is machined from 8620 steel and has a phosphate finish. The bolt is made from mil-spec Carpenter 158 steel and is high-pressure tested and magnetic particle inspected.
Finally, the rifle is outfitted with a standard A2 flash hider, A2 pistol grip, and M4 collapsible buttstock.
All-in-all, it’s a pretty standard but high-quality rifle. My only real gripe is the price- this thing comes in at about $1,400. While you get a great rifle, it’s a little hard to cough up that much for a pretty basic gun.
See It HereDaniel Defense DDM4V11
Expect top-shelf materials, construction methods, and performance features from Daniel Defense. With their DDM4V11 pretty much everything is updated and improved over more standard mil-spec type fare. Though at this price point, it should be. You’ll find upgraded triggers, bolt carrier groups, handguards, and barrels. In addition, expect small things like upgraded muzzle devices and high-quality furniture.
Daniel Defense has a strong reputation for making high-end AR-15 parts and accessories. Their DDM4V11 and DDM4V11 PRO certainly live up to that reputation. In fact, they may be the best off-the-shelf AR-15 rifles I’ve ever shot. The quality and attention to detail on these rigs is incredible.
The DDM4V11 model tested here has an 18″ cold hammer forged, 4150 CMV steel, chrome lined, and phosphate barrel with a 1:7 twist rate. The low profile gas block and rifle length gas system mean this thing shoots very smoothly and accurately.
This thing is light, too. At just 7.53 pounds it’s not a huge burden to carry around when your at the range all day or during a competition.
As far as the upper and lower receivers go, they are constructed from 7075-T6 aluminum as you would expect. The lower receiver has a flared magazine well that makes loading magazines a breeze.
You also get Daniel Defense’s Gen 2 Muzzle Climb Mitigator, which is a hybrid compensator and muzzle brake. It works very well in my experience.
In addition, you get a full complement of Daniel Defense furniture, which includes their awesome SLiM Rail, buttstock, pistol grip, and magazine.
See It HereFN 15 Tactical II
The FN 15 Tactical II is just one of many exceptional AR-15 models by FN, but it’s the one I feel most comfortable reviewing. Why? Because I own this exact weapon and I’ve certainly run it through its paces.
Like the other guns here, accuracy is superb. I’m able to achieve sub-2″ groups at 100 yards on a regular basis. I’ll chock it up to FN’s proprietary free float rail system and basic, but crisp combat trigger.
The barrel is chrome-lined, cold hammer forged and machined from 4150 CMV steel. Finally, it’s tipped with FN’s three-prong flash hider. This combination of features offers the greatest performance and durability, and it’s exactly what I look for in a barrel, regardless of manufacturer.
The lightweight rail is very nice and features a proprietary locking and alignment system that make this thing rock solid. It also has plenty of M-LOK sections that allow you to attach any accessories you want. Speaking of accessories, included with the rifle is a Magpul MOE grip, Magpul MOE SL buttstock, and 30 round Magpul PMAG.
The bolt carrier group is made from 8620/Carpenter 158 steel and phosphate finished. Everything is high-pressure tested and magnetic particle inspected to ensure ultimate reliability and durability.
All-in-all, this is a great gun and one I would recommend to anyone that wants a no-nonsense workhorse for the range or home defense.
See It HereRuger AR-556
The Ruger AR-556 is another high-value weapon with a strong pedigree. It also includes a few choice upgrades that make this rifle an interesting option.
Like the AC-15 and M&P 15 Sport II, accuracy is exceptional despite the drop-in handguard and mil-spec trigger. 2″ groups are easily obtainable at 100 yards through a scope.
Like the other two, this is also a very mil-spec type rifle, although there are a few twists like I mentioned before. It has a proprietary front sight post with a quick disconnect hole that is compatible with a number of sling options. As a bonus, it still maintains a standard F-height for co-witnessing with optics.
It also comes with a nice upgraded pistol grip. Everything else is pretty standard, however, and includes an A2 style flash hider, polymer hand guard, and M4 style collapsible buttstock.
The barrel is phosphate finished, but isn’t chrome lined, high-pressure tested, or magnetic particle inspected as far as I can tell. This, I’m assuming, is a cost-cutting measure by Ruger. It is made from cold hammer forged 4140 steel and has a 1:8 twist rate and extended feed ramps.
Both upper and lower receivers are forged from high-quality 7075-T6 aluminum. The upper receiver is not T-marked but has a forward assist button and dust cover, unlike some other budget AR-15s. The lower receiver features a flared magazine well to allow for easier magazine changes.
The chrome-lined, semi-auto bolt carrier is machined from 8620 steel and has a phosphate finish. The bolt is made from mil-spec Carpenter 158 steel but is only magnetic particle inspected. Also included with the rifle is Ruger’s proprietary rear sight and one 30 round magazine.
Overall, this is a great gun but with similar trade-offs to the Smith & Wesson M&P 15 Sport II. The barrel is constructed from weaker 4140 steel. The proprietary front and rear sights are excellent, however, and the quick disconnect point is very convenient.
See It HereSmith & Wesson M&P15 Sport II
Smith & Wesson’s M&P15 Sport II is a very popular rifle and a nice upgrade over their previous model. When you consider the features and price, there’s no wonder why this is such a coveted starter rifle.
Like the AC-15 above, accuracy is very good with this rifle despite the drop-in handguard and somewhat poor trigger. Again I was able to maintain less than 2″ groups through a scope.
Also, like the AC-15, this rifle is a mil-spec style all the way. It has an A2 flash hider, F-marked front sight post, polymer hand guard, A2 pistol grip, and M4 collapsible buttstock. Though, the trigger feels a bit more spongy and reset is not as positive as a lot of other mil-spec ones.
The barrel itself features a durable nitride finish inside and out but is not magnetic particle inspected or high-pressure tested. It’s made from 4140 steel, has a 1:9 twist rate, and extended feed ramps. I also noticed significant machine marks on the barrel underneath the handguard.
Both upper and lower receivers are forged from high-quality 7075-T6 aluminum. The upper receiver is T-marked and has a forward assist button and dust cover, unlike the previous version. The lower receiver features a flared magazine well to allow for easier magazine changes and an integral trigger guard.
The chrome-lined, semi-auto bolt carrier is machined from 8620 steel and has a phosphate finish. The bolt is made from mil-spec Carpenter 158 steel but is only magnetic particle inspected as far as I can tell. Also included with the rifle is a Magpul MBUS rear sight and one 30 round PMAG magazine.
Overall, there are some trade-offs with this rifle, which is to be expected at this price point. The two reservations I have with this weapon are barrel material (it’s 4140, not 4150) and the trigger. But judging from other reviews and my own experience it is a very reliable weapon and definitely worth a look.
See It HereUltimate AR-15 Buying Guide
The AR-15 is made of two major components – the upper and lower receivers. Each of these components is further broken down into several individual parts.
To simplify this guide, I organized it to focus on the upper and lower receivers, as well as their associated parts, separately.
Doing it this way not only provides a logical flow and structure, it will also help keep things straight in your head. Referencing a section, later on, will be dead simple, too.
Obviously, each component has unique considerations to account for, but there are a few common things that apply to everything. Top-shelf materials, finishes, and quality control are crucial. And that’s what I’ll focus on the most moving forward.
An inferior AR-15 simply won’t suffice, especially when your life is on the line. So it makes sense that factors that affect reliability and durability will receive the most attention.
But that doesn’t mean you have to pay through the nose for quality. As you saw in the previous sections, a good AR-15 can be purchased at a reasonable price.
So, let’s attack this topic head-on. There’s a lot to learn but I hope to make it as simple and straightforward as possible. I’ll begin with the upper receiver and its components first.
Upper Receiver
The upper receiver, like the name implies, is the foundation for the top half of the AR-15. It houses the bolt carrier group and charging and is threaded on the forward portion to receive the barrel, handguard, gas system, and muzzle device.
In this context, it is referred to as a “stripped” upper receiver. But in the case of a complete rifle, the upper receiver will be fully assembled and include the components mentioned above – this is called a “complete” upper receiver.
There are two common types of stripped AR-15 upper receivers – forged and billet. Forged receivers are by far the most popular and its combination of strength and value is hard to beat.
Forging is a process where hot metal is hammered into the general shape of an upper receiver and produces a stronger part than a billet or cast equivalent.
As the metal is molded during the forging process, its internal grain deforms to follow the shape of the part. As a result, the grain flows continuously through the part giving rise to a piece with improved strength characteristics.
A billet upper receiver is as much a piece of modern art as a hardcore firearms part. CNC machines carve each receiver from a single aluminum block in a process that can take hours. After everything is done, you’re left with a rugged and good looking part for your AR-15.
The billet manufacturing process does offer room for greater aesthetic changes and performance tweaks that are very hard to find in forged parts. But, they are inherently weaker and generally more expensive.
Upper receivers are traditionally made from 6061-T6 or 7075-T6 aluminum alloy, with 7075-T6 being the tougher, more durable option. 7075-T6 is ubiquitous among AR-15 parts and accessories manufacturers, it’s also the standard for military applications.
Finally, the upper receiver is finished with a protective coating that guards against abrasions, chemicals, and oxidation. Hard coat anodizing is the most popular finishing technique although a lot of high-quality proprietary coatings, like Cerakote, are available too.
Recommendation: Look for an upper receiver that is made from 7075-T6 aluminum. While 6061-T6 is acceptable for this application, 7075-T6 offers better value when you consider it’s superior durability. Which type of receiver you select (forged or billet) is a matter of preference, but understand the pros and cons of both. Finally, the receiver should have a high-quality, durable finish – hard coat anodizing or better.
Upper Receiver Parts
The upper receiver has very few actual parts. The main components are the ejection port cover, forward assist button, charging handle and various springs, pins, and roll pins that hold everything together.
Functionally, there isn’t much difference between manufacturers as each component is standardized and should fit any upper receiver regardless of supplier.
However, some companies make proprietary parts, which is often the case with billet receivers. In addition, you may find some aesthetic differences, although everything should fit and operate the same. It’s just something to be aware of when shopping for an AR-15.
Charging handles are a common upgrade and many people find larger or ambidextrous latches make charging their weapon easier. If you are left-handed or have trouble pulling the charging handle to the rear, this is something you want to consider.
Similar to the upper receiver itself, the parts should have a quality finish that protects against damage. The ejection port cover, forward assist, and charging handle will have the same finishes as the receiver (hard coat anodizing or similar.)
Recommendation: As a rule, stick to a reputable company when choosing an AR-15. This is the best way to ensure you’re upper receiver parts are top quality. Leading manufacturers produce a product that is tightly machined and within specifications. Aesthetic and ergonomic choices are up to you, but the same rule applies.
Feed Ramps
This is a small consideration, though it can be a confusing subject. Let’s start with the basics.
When the AR-15 is fired and the spent case is ejected, the feed ramp functions to direct a new cartridge from the magazine into firing position. The need for the cartridge to slide both forwards and upwards along the feed ramp and into the chamber is the primary design consideration.
Feed ramps are a function of both the upper receiver and the barrel itself. There are two common types of feed ramps for the AR-15- standard and extended.
Standard feed ramps are only machined into the barrel extension, which is the part of the barrel that fits into the upper receiver. A standard feed ramp barrel extension requires a matching upper receiver that has no additional machining done. Standard feed ramps are sometimes referred to as rifle, A3, or A4 profiles.
Extended feed ramps expand beyond the barrel extension and into the upper receiver. An extended feed ramp barrel extension requires a matching upper receiver that is machined to match. This profile is meant to help feed rounds more reliably by increasing the usable surface area of the feed ramp itself. Extended feed ramps are commonly referred to as M4 profiles.
Recommendation: While this isn’t a big concern if you’re buying a complete AR-15, it’s something to keep an eye on. A mismatched upper receiver and barrel can cause feed issues that decrease reliability. I recommend extended feed ramps where available, as this is the improved version, but I have never had an issue with standard feed ramps.
AR-15 Barrels
The barrel is arguably the most critical component of your AR-15. As such, there are a number of considerations that can affect accuracy, longevity, and function that you should know about. I’ll provide a quick primer here and expand on each consideration in the sections that follow.
The barrel is secured to the upper receiver with a barrel nut and has a barrel extension, or lug, that fits into the upper receiver. This barrel extension is precisely machined to match the upper receiver and bolt carrier group. In addition, the barrel extension, along with the bolt carrier group and barrel itself, are machined to accept a specific cartridge.
The standard cartridge for the AR-15 is 5.56 NATO and .223 Remington. While these rounds are very similar, they are not compatible in some instances. A barrel chambered for .223 Remington can safely shoot only that round. While a barrel marked 5.56 NATO or .223 Wylde can shoot both rounds reliably.
The AR-15 can be configured to fire other popular rounds as well. At a minimum, this will require a barrel, bolt carrier group, and magazine that is compatible with these rounds.
While we’re on the topic of AR-15 ammunition, there’s something else you should be aware of: twist rate. The AR-15 barrel has grooves in the internal surface, called rifling, which impart a spin to the projectile. The measurement of the distance in inches it takes for the rifling to make a complete revolution inside the barrel is called twist rate.
The intent of rifling is to stabilize the projectile as it exits the barrel, making it much more accurate. The twist rate will affect how well it stabilizes depending on weight and length of the projectile. For example, a tighter 1:7 twist rate will stabilize heavier 77 grain ammo better than a looser 1:12 twist rate barrel.
Barrels are available in a range of lengths from 7.5″ to 24″ or more depending on your application and state or federal laws. Common lengths are 7.5″ and 10.5″ for pistols, 14.5″ and 16″ for carbines, and 18″ and 20″ for rifles. However, any length is possible.
Barrel length also influences gas system length. The AR-15 cycles by leveraging energy in the form of rapidly expanding hot gas that builds up behind the projectile. A small amount of gas is siphoned through a gas port located near the end of the barrel and travels down the gas tube and enters the gas key on the bolt carrier group.
The distance between the gas port and the end of the barrel, as well as the gas port and the gas key, will affect dwell time and how smooth your weapon operates. That, in turn, effects which components you select as you try to mitigate potential problems.
Finally, you need to consider barrel materials, linings, and finishes. The barrel endures a tremendous amount of heat and stress, so it needs to be well constructed to avoid premature wear and failure.
Common barrel alloys include 4140 and 4150 carbon steel, as well as 410 and 416 stainless steel. Popular linings include chrome and melonite, and popular finishes include phosphate, melonite, nitride, or any number of proprietary coatings.
Military specifications call for a chrome lined 4150 CMV barrel. 4150 CMV is a variation of standard 4150 steel that adds additional vanadium and carbon to make it bit more resilient in extreme environments and temperatures. 4150 steel, in general, is stronger than 4140 steel and the best choice for most applications.
Stainless steel is increasingly popular because of its reputation for improved accuracy compared to carbon steel. It’s machining properties and wear characteristics offer a higher resolution barrel that provides peak accuracy for those who need it. However, stainless steel barrels are pricey and may not offer the best value. 410 or 416R steel is the best choice if you want a stainless barrel.
Recommendation: As you can see, there is a lot to think about. I’ve only outlined the basics here. And, rather than include everything in one monster section, I’ll expand a bit more below. But as a rule of thumb, the barrel should come from a reputable manufacturer and be made with the best materials possible- I recommend 4150 carbon steel, 410 stainless steel, or 416R stainless steel. In addition, I prefer a chrome or melonite lined barrel as it extends the life and performance of the barrel greatly. The barrel should have a high-quality finish to protect against the elements, as well. One barrel isn’t better and any other if there is no quality in the manufacturing process. Everything else like barrel profile, length, and twist rate is rather subjective and will depend on your application.
AR-15 Barrel Profiles & Contours
The AR-15 is a mature, modular platform and is viable for a host of military and civilian applications. As such, a lot of barrel profiles are available, though one may be preferable to another depending on your use case.
Be aware that there can be a lot of variation between manufacturers as far as barrel profiles and contours are concerned. For example, manufacturer A’s lightweight barrel may be machined for a .750″ gas block while manufacturer B’s is machined for a .625″ gas block. Nothing is set in stone.
It’s things like that, which make a discussion about barrel profiles difficult. So in an effort to make things less confusing, I’ll break down barrel profiles into four categories: lightweight, government, medium, and heavy profiles.
The struggle is real, so how do you choose which AR-15 barrel profile is best? Well, let me run down the categories and talk about their intended application, benefits, and trade-offs.
Lightweight Profile
Like the name implies, this profile is meant to be lightweight, easily maneuverable, and to reduce fatigue. Rucking a heavy weapon can be hell, and since a lot of the AR-15’s weight is concentrated in the barrel it is an ideal candidate for weight reduction.
A lightweight barrel can also change the balance and overall feel of the weapon by making it less front heavy. This is also beneficial if you do a lot of firing without support.
On the other hand, a lightweight barrel will experience heat soak sooner, which reduces accuracy under sustained fire. Though, while this is something I’ve experienced personally, it was only after several hundred rounds that the problem occurred. Needless to say, most shooters will not have an issue.
Another common concern is barrel life, though I have not seen a lightweight barrel fail prematurely due to the profile. Anecdotally, it could be a problem since there is less material making the barrel weaker overall.
I’ll also include featherweight and pencil barrels in this category. The barrel wall thickness is reduced even further for featherweight barrels compared to a typical lightweight barrel. However, this may limit the type round you can safely fire due to the extreme pressure inside the barrel.
Pencil barrels are typically machined for one thickness (usually .625″) down the entire length of the barrel. While some manufacturers taper the barrel moving toward the throat, there are no built-in contours except for gas block provisions.
Government Profile
This profile gets its name from its resemblance to military, or government, issued weapons. These profiles vary greatly but are usually a mix of lightweight and medium or heavy profiles.
For example, an M4 profile barrel will have a lightweight or medium profile underneath the handguard and transition to a medium or heavy profile after the gas block.
Sometimes, government profile barrels are provisioned for grenade launchers or have a bayonet lug. This is important for military or law enforcement applications, but less so for the civilian market.
Government profiles are a good compromise between lightweight and medium or heavy barrels. They offer a lighter weight option but mitigate potential heat soak problems.
Again, there is a lot of variation here but a few common government profiles are M4, M4A1, A1, A2, and SOCOM. Each has slightly different characteristics and it would be a bit cumbersome to list them here, but here is a good resource if you’re interested in the differences.
Medium Profile
This profile is almost exactly the same as a lightweight barrel, except it is, well, heavier. As such, this is a good all-purpose barrel profile that will help mitigate heat soak without adding a lot of weight.
Additionally, medium profile barrels don’t have the same perceived reliability issues that a lightweight barrel has. However, like I said before, I think this is a case of negativity bias. And I’m sure thousands of AR-15 shooters will agree that lightweight barrels are perfectly serviceable.
Nonetheless, a precisely machined medium profile barrel made with top-shelf materials will perform exceptionally well in most circumstances.
Heavy Profile
Heavy barrels are the next step up from medium barrels in both size and weight (there’s a pattern here.) They have the greatest barrel wall thickness and provide the best performance in sustained or full auto fire where heat soak is a real problem.
Commonly, heavy barrels, or HBAR barrels, will be 1″ in diameter under the handguard and step down to .750 at the gas block. Another variation, called a bull barrel, will often be 1″ in diameter and only step down to .936″ or .938″.
Some will argue that heavy barrels offer greater accuracy as a result of increased rigidity and reduced harmonic distortion. However, that is a complicated subject and, suffice it to say, that’s only a small part of the equation.
Most people will not see a consistent improvement in accuracy between a heavy barrel and it’s lighter brethren. Though, a heavy barrel may help you stay on target and reduce felt recoil. Where you will see the most benefit is with good ammo and practice.
Recommendation: Which barrel profile you choose will depend on your use case and is highly subjective. My personal preference is for an M4 or SOCOM government profile barrel because they provide exceptional performance under sustained fire without a lot of extra weight. However, I can recommend any of the barrel profiles listed here. As long as the barrel is precisely machined from great materials, you really can’t go wrong.
AR-15 Barrel Length
Selecting a barrel length seems simple, but it’s actually a rather nuanced subject. Barrel length will affect muzzle velocity, flash intensity, sound levels, and, in some cases, accuracy. These are all important considerations, so let’s explore these topics and possibly dispel some myths along the way.
A longer barrel is not inherently more accurate than a shorter barrel. Quality will affect intrinsic accuracy much more than length. However, a longer barrel may be better in terms of practical accuracy. Since it is longer and therefore heavier, it is easier to stay on target from an unsupported position.
In addition, the longer sight radius (distance between front and rear sights) makes it easier to shoot a long barreled rifle accurately. But, this is a moot point when using optics or shooting from a bench rest.
Longer barrels preserve linear velocity and produce higher rotational velocity, which will result in better gyroscopic stability of the bullet. The 5.56 NATO round was originally designed for a 20″ barrel and achieves optimal performance at this length. But does that mean a shorter barrel is ineffective? Not at all.
In fact, typical carbine length barrels from 14.5″ to 16″ easily retain enough energy to produce a lethal wound channel out to 400 yards. And when you consider the ease of carrying and maneuverability in close quarters, a shorter barrel may be your best option.
However, significantly shorter barrels in the 7.5″ to 10.5″ range can introduce a number of undesirable effects when paired with the 5.56 NATO round. The low linear velocity can make rounds unstable or lose so much kinetic energy that they are no longer effective at longer distances.
In addition, shorter barrels have higher uncorking pressures, which increase sound pressure levels and flash intensity dramatically. Increased pressure and over gassing also leads to more forceful cycling that can reduce the lifespan of certain parts. As such, gas management is critical for shorter barrels.
Recommendation: When it comes to barrel length you have to manage expectations and balance the need for maximum velocity at long range with portability. But like I tried to impart above, the 5.56 NATO round is more than capable inside 400 yards with a barrel as short as 14.5 inches. For my money, a 16″ or 18″ barrel is the sweet spot. Anything shorter will require you to permanently attach a muzzle device (14.5″) or go the pistol or SBR route. Anything longer can be cumbersome or isn’t even necessary.
AR-15 Barrel Twist Rate
Rifling is a series of helical grooves machined into the bore, which impart a spin to the projectile. The distance, in inches, it takes for the rifling to make a complete revolution inside the barrel is called twist rate.
Twist rate is most commonly expressed as a ratio like 1:7 (1 in 7) or 1:9 (1 in 9.) This simply means that a projectile will make one (1) complete turn inside the barrel for every seven (7) or nine (9) inches of travel.
So why does twist rate matter? The spin imparted by the rifling serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.
However, there is such a thing as too much spin. Certain bullet types may even come apart if the twist rate is too fast. While longer, heavier bullets may not stabilize enough if the twist is too slow. In both cases, accuracy may be negatively affected.
So to keep things simple, I put together a table that references twist rate, intended application, and bullet weight. This table applies to 5.56 NATO and .223 Remington only:
| Twist Rate | Application | Bullet Weight |
|---|---|---|
| 1:12 | Varmint Hunting | 40-55 GR. |
| 1:9 | General Purpose | 40-62 GR. |
| 1:8 | Medium To Long Range | 62-77 GR. |
| 1:7 | Long Range Match | 62-90 GR. |
The most popular twist rates are 1:9 and 1:7. These twist rates specially offer great performance and accuracy when using a wide range of commercially available ammunition.
Recommendation: When trying to figure out which twist rate is best, first consider what the AR-15s use case is as well as the type and weight of ammunition you’ll be using. Heavier, longer loads require a faster twist rate while shorter, lighter loads will need a slower twist rate. For a good all around twist rate I recommend 1:9 or 1:8. A 1:7 twist rate is also good, especially if you shoot a lot of heavier match ammo or military surplus rounds.
AR-15 Barrel Materials
When it comes to barrel materials, you really have only two choices – carbon or stainless steel. There are other barrel materials, but their use isn’t widespread and in some cases, they can be prohibitively expensive. In the interest of time, I won’t discuss them here.
Carbon and stainless steel are exceptionally strong and durable, making them ideal materials for use in barrel manufacturing. In addition, steel is inexpensive, readily available, and relatively easy to machine – all factors that keep costs down for consumers.
Both carbon and stainless steel are alloys, which means they contain trace elements that improve strength and corrosion resistance, among other characteristics. For example, stainless steel contains significant amounts of chromium, which is an exceptionally hard material that protects against corrosion and prevents rust.
The amount of trace elements ultimately determines how durable or corrosion resistant an alloy will be. In addition, the quenching and tempering process will significantly impact the hardness and stability of the material.
In some cases, it’s pertinent to trade strength for other benefits. As the amount of carbon in a steel alloy rises, for example, it becomes harder and stronger, but less ductile and more difficult to machine.
The addition of these trace elements can also increase prices significantly. When you talk about tougher, high-end materials, increased wear-and-tear on tools and the need for experienced professionals needs to be factored into the cost.
Let’s talk about the most common carbon and stainless steel alloys. I’ll break down their properties and speak to why you may want to choose one over another.
4140 Steel
4140 steel is often considered a lesser choice when it comes to AR-15 barrels. However, it is an extremely capable material and I’m willing to bet most people won’t find any difference in performance between it and 4150 or stainless steel.
4140 steel contains less carbon than 4150 steel, as such, it has slightly less tensile strength but slightly more yield strength. Other than that, they are virtually identical.
In general, 4140 steel has high fatigue strength, abrasion and impact resistance, toughness, and torsional strength. Altogether this is a great material and it’s used extensively, especially for budget barrels.
4150 Steel
As I said above, 4150 steel is almost exactly the same as 4140 steel. However, it does have a few characteristics that make it marginally better for AR-15 barrels.
Like 4140 steel, 4150 steel has high fatigue strength, abrasion and impact resistance, toughness, and torsional strength. However, because it has a little higher carbon content it is a bit stronger and has a slightly higher melting point and thermal conductivity coefficient. Though, the difference is rather minuscule.
This material is only slightly better than 4140 steel, but it would be my preference if I had to choose between the two. I’ll take the extra strength when I can get it.
4150 CMV Steel
4150 CMV steel is the same alloy as 4150 steel with the addition of an element called vanadium. Vanadium improves strength and corrosion resistance when added to various alloys, which makes it perfect for AR-15 barrel manufacturing. In fact, this is the type of steel required for military applications.
It’s also the choice for many high-end barrel manufacturers and my preferred material where possible. The improved strength and corrosion resistance offer peace of mind, and the price, in general, is very reasonable when compared to other carbon steel alloys.
410 Stainless Steel
There are two main benefits to stainless steel barrels. First, they are more corrosion resistant than an unlined carbon steel barrel. Second, stainless steel is harder and more resistant to heat than carbon steel when properly tempered. That’s not to say stainless steel won’t rust or corrode if neglected, though.
Grade 410 steel is a general-purpose stainless steel that containing 11.5% chromium, which provides good corrosion resistance properties. It’s also very heat resistant, offering good scaling resistance at temperatures of up to 1200°f.
Overall, this is an extremely capable material that will be very durable and long-lived. However, it is physically very hard and difficult to machine, so you tend to pay a premium.
416 Stainless Steel
416 stainless steel is chemically very similar to 410 stainless, but with more sulfur content. The additional sulfur makes the material easier to machine but increases the risk of manganese sulfide inclusions.
These inclusions contribute to a phenomenon called temper embrittlement, which significantly degrade ductility and impact resistance, especially at extremely cold temperatures.
In addition, this sulfur addition lowers the corrosion resistance, weldability, and formability to below that of grade 410 stainless steel. As such, I generally don’t recommend this material if you have a choice.
416R Stainless Steel
416R is a very popular material used in AR-15 barrel manufacturing. It is chemically similar to grade 416 steel but has less sulfur content and adds molybdenum. These additions are meant to keep some of the benefits of grade 416 stainless steel (mainly ease of machining) while mitigating the temper embrittlement and ductility problem I outlined above.
410 and 416R are your best bet when it comes to stainless steel barrels. They both are extremely durable and heat resistance – features important to an AR-15 barrel.
For more information on any materials check out the AZO Material website.
Recommendation: My choices for best barrel materials are 4150 CMV, and 416R. Really, there’s not a strong argument to go with anything else since prices and availability are comparable regardless of the material. Even budget options, like the Aero Precision AC-15 listed above, come with a chrome lined 4150 CMV barrel. Though, the other materials are more than capable, and, in my eyes, it isn’t a bad choice as long as you understand their shortcomings.
AR-15 Barrel Finishes, Linings & Testing
I kept this section for last, but that doesn’t mean it should be an afterthought. On the contrary, the type and quality of finishes and linings are of paramount importance. In addition, high-pressure testing and magnetic particle inspection are two tests that set a high-quality barrel apart from a lesser product.
Personally, I would hesitate to purchase a rifle if the barrel hasn’t been sufficiently tested or properly lined. These processes go a long way in ensuring a barrel is stable and free from imperfections that may reduce its lifespan.
There are a number of linings and finishes available, and I’ll outline a few here. In addition, I’ll briefly talk about the high-pressure testing and magnetic particle inspection process.
Chrome Lining
Chrome is applied to the barrel bore and chamber because it protects against corrosion, heat, and it provides a longer service life. If you subject your gun to corrosive ammo, rain, or if you live near salt water, a chrome lined barrel may be the way to go.
Since it is almost impossible to apply uniformly, there are often slight imperfections that may affect accuracy. For most people, however, this isn’t something to be concerned with and the difference is often negligible. It’s worth the tradeoff in most cases for the reasons I listed above.
A non-lined barrel will work, as long as you properly care for the weapon. Properly cleaning and lubing your barrel will ensure it lasts for a long time regardless if it is lined or not.
Nitride
This is a popular finish that can be applied to both the inside and outside of the barrel. Like chrome, a nitride lining will protect against corrosion, heat, and will give a longer service life. However, the process provides for a more uniform application and mitigates the slight accuracy issues experienced with chrome.
From my experience, this is an excellent finish and a great alternative to chrome. Nitride actually changes the molecular structure of the steel and case harden it. It also adds lubricity, which makes it a good finish for bolt carrier groups as well.
Note that nitride and Melonite are two names for the same process. It’s common for AR-15 manufacturers to refer to their coatings and linings by a proprietary name. Generally, these names are given to an already established process, so it’s important to do your research before making a purchase. That way you know exactly what you’re getting.
Phosphate
Phosphate finishes are ubiquitous because they are relatively cheap to apply and provide awesome corrosion protection and improved friction properties of sliding components. This is also the type of finish you will find on mil-spec barrels.
The process of applying a chemical phosphate coating is rather simple. The barrel is submerged into a heated phosphoric acid solution containing dissolved zinc or manganese phosphate salts. When the steel is placed in the solution, a simple reaction takes place, causing the dissolved salt to fall out of solution and be precipitated on the surface.
High-pressure Testing (HPT)
High-pressure testing is a process where the barrel is pressurized to ensure it meets or surpasses SAE and AISI specifications for the material. The intent is to guarantee the material is stable and will not fail prematurely.
AR-15 barrels may be individually tested or tested in batches. Batch testing simply involves selecting one or a few barrels from a production run and testing them. If they pass, the rest of the barrels are given the green light.
Of course, individually testing each barrel is best. However, batch testing saves time, money, and is better than nothing at all. Unfortunately, the type of testing is not readily disclosed in most cases.
Magnetic Particle Inspection (MPI)
Magnetic particle inspection is an excellent method to investigate near-surface defects in barrels and other ferromagnetic materials. The process involves inserting the barrel between two poles of an electromagnet and saturating it with a suspension of magnetic particles. An ultraviolet light is then used to inspect the surface looking for visible cracks or other defects.
Like high-pressure testing, magnetic particle inspection can be done individually or in batches. If a barrel is found to have significant defects it will be discarded.
Recommendation: Like I stated before, proper testing along with a good quality finish and the lining is important. These processes ensure the barrel is battle ready and free from defects that can negatively impact its lifespan. In addition, they protect against outside elements, which will further degrade the barrel. I prefer a nitrided or chrome lined and phosphate barrel over an unlined barrel. That isn’t to say an unlined barrel is bad, it just needs more attention and care. Though, the benefits of a lined barrel generally outweigh those of an equivalent unlined one.
AR-15 Muzzle Devices
Muzzle devices are not just about looks, they actually serve an important function. Some muzzle devices perform one specific task, like suppress flash intensity or reduce felt recoil. Other devices, called hybrids, can perform more than one function. A common example of a hybrid device is the A2 flash hider, which is part flash suppressor and compensator.
There are a lot of devices on the market, so it’s important to differentiate what they do. In this section, I’ll outline the types of devices available to you.
Flash Suppresor
A flash suppressor, like any muzzle device, is attached to the end of the barrel. Its purpose is to reduce flash intensity by rapidly cooling and dispersing the hot gases that exit the barrel.
Reducing flash intensity mitigates the risk you will be temporarily blinded by the flash when shooting in low-light conditions. It also reduces your visual footprint and makes you less visible to others.
Birdcage, three-prong, and four-prong devices work very well, and it’s the way to go if the flash intensity is your main concern. In addition, these devices are usually pretty cheap making a great option if you’re on a budget.
Muzzle Brakes
A muzzle brake is a type of device that is machined in a certain way as to redirect gases to counter recoil and muzzle flip.
In general, a reduction in recoil will make your weapon more comfortable to shoot and help you stay on target by reducing muzzle rise. In some cases, you can experience up to a 50% reduction in felt recoil.
These devices do not provide much flash suppression and tend to be very loud, however. This is because the sound, flash, and pressure normally projected away from the shooter are now partially redirected outward, to the side, or sometimes at partially backward angles toward the shooter.
This is the type of muzzle device you’ll want if recoil is a major concern for you. The difference is quite dramatic and in some cases, it will be like shooting a totally different gun. Understand the drawbacks to a device like this, though, mainly the increased flash intensity and sound pressure levels.
Linear Compensators
Like muzzle brakes, these devices are machined to redirect gases to counter muzzle flip. In this case, the gas that is ported upward and outward counteracts the natural rise by pushing back in the opposite direction. But, unlike muzzle brakes, this type of device is not strictly meant to reduce felt recoil.
Since a compensator only reduces muzzle flip, they are not very popular. In general, you will find devices that are combination compensator and flash hider or muzzle brake.
Hybrid Devices
As mentioned above, hybrids are a combination of more than one type of muzzle device. The intent is to offer the best of each type of device. That includes good flash suppression, recoil management, and muzzle rise compensation.
A typical example of a hybrid device is the military-style A2 flash hider. It is a birdcage design flash suppressor but the bottom tines are not machined out. Birdcage type flash suppressors are great for minimizing flash intensity and the solid bottom directs gases upward, which helps keep the muzzle down.
Other hybrid devices can contain any combination of devices. This is a popular category of muzzle devices, for obvious reasons, and one I would recommend for most shooters.
Recommendation: Muzzle devices are a small but important consideration when choosing an AR-15. But, don’t let it define what you choose, because it’s pretty simple to change out later on down the line. Most budget AR-15s come with a standard A2 style flash hider, which is simple and effective. You will have to spend a bit more to get something different. Personally, I’m a fan of hybrid devices. There are some great parts out there that offer really stellar performance.
AR-15 Gas System
The AR-15s direct impingement gas system is simple and robust. It operates by leveraging the hot, rapidly expanding gases that build up behind the projectile when you fire a round.
The gas is siphoned off through a small gas port located towards the muzzle, it moves through the gas block, down the gas tube, and into the gas key located on the bolt carrier.
The energy from the gas pushes the bolt carrier group rearward, simultaneously ejecting the round. As the buffer tube pushes the bolt carrier group back into battery, it strips a new round from the magazine and is ready to fire again.
Pretty easy, right? It is but there are a few downsides to a system like this. First, since the AR-15 relies on consistent gas pressure to operate, the entire system needs to be precisely machined, leaving little room for out of tolerance parts. A loose or misaligned gas block, for example, means gases will leak out leaving little energy to cycle the action.
Second, the super tight tolerances also mean that your weapon needs to be impeccably maintained. Carbon buildup and debris can severely diminish the reliability of your weapon, and venting hot gases into the bolt carrier group exacerbates the issue.
The other alternative is a short stroke piston system, which uses the gases to drive a small piston that cycles the action. These systems can be prohibitively expensive, however, and there are concerns about reliability in many cases. If you want a piston driven AR-15 it’s best to go with a very reputable manufacturer, which will help guarantee reliability.
Now that you know a little bit about how the AR-15 direct impingement gas system works, let’s take a look at a few of the big details you will need to consider.
Gas Blocks
The gas block is positioned over the gas port and straddles the barrel. Its purpose is to manage the flow of gas through the gas port down the gas tube and into the gas key located on the bolt carrier. It’s a simple, but critical component.
Since it interacts with very hot, high-pressure gas, the gas block has to be made from a sufficiently durable material. Carbon steel, stainless steel, or even titanium are best suited for this application.
Aluminum gas blocks are available, but I generally don’t recommend them. Aluminum is just too soft and can erode faster than the aforementioned materials. Also, aluminum’s expansion rate is significantly different from most barrel materials, which may cause fitment issues after prolonged use.
An adjustable gas block may be required for some applications. Adjustable gas blocks let you fine-tune the amount of gas that travels through the system by simply adjusting a valve. This is great for short gas system setups like AR-15 pistols or carbines. In which case, hard cycling, extraction, and ejection problems can be alleviated.
The last part to consider is the method by which the gas block is attached. It should fit very tightly around the barrel to stop any gas from leaking out. Preferably, the barrel will be dimpled and the set screw properly torqued – this will prevent the gas block from moving.
Gas System Length
Typical gas system lengths are rifle, mid, and carbine. This simply indicates the distance between the gas port and the gas key on the bolt carrier. The gas system length will impact how well the system operates and can change the nature of the weapon dramatically.
This is a very nuanced issue, but to better understand gas system length and exactly why it matters let’s run through the lengths in order from longest to shortest.
Rifle Length Gas System
The original M16 and AR-15 were built to fire a 5.56 NATO round through a 20″ barrel with a long rifle length gas system. And this platform performs very well, offering a combination of peak velocity from the round and very smooth action. In this case, the gas system length has a lot to do with that.
The longer barrel and gas system means there is more room for the expanding gases behind the bullet as it passes the gas port, which effectively reduces the port pressure. This translates into softer action and reduced felt recoil.
Before going any further, though, I think it’s pertinent to introduce another factor in this equation – dwell time. Dwell time is determined by the length of the barrel after the gas port and significantly affects port pressure.
After the projectile passes the gas port it has to remain in the barrel for a short amount of time so that a sufficient amount of pressure can build. If the dwell time is too long, too much pressure will build and the opposite is true if the dwell time is too short.
This relationship between gas system length and dwell time is important to understanding the nature and limitations of the AR-15 platform. Compared to a rifle length gas system, a 20″ barrel with a carbine length system will exhibit significantly higher port pressures because of the increased dwell time.
Mid-length Gas System
This gas system length is very popular and is a good compromise between a longer rifle length gas system and a shorter carbine length system when using a barrel between 18″ and 14.5″ long.
Because it is slightly longer, a mid-length gas system offers smoother action than a shorter carbine length gas system. Just like the rifle length system it has more room behind the projectile for expanding gases, which effectively reduces port pressure.
Again, it’s important to understand dwell time and how that may affect port pressures when choosing a barrel length. A shorter barrel will have less dwell time than a longer barrel, for example.
Carbine Length Gas System
This is the shortest of the traditional gas system lengths. Originally designed for weapons with a 14.5″ barrel, it is also pretty standard on more civilian friendly 16″ models. And, although very reliable, it does present a problem.
A longer 16″ barrel will inherently have a longer dwell time than a 14.5″ barrel, which translates into higher port pressures and harsher action overall. This is certainly something to keep in mind when buying an AR-15 with a 16″ barrel and a carbine length gas system.
This phenomenon, along with the proliferation of 18″ weapons, has really driven the popularity of mid-length systems. Manufacturers recognize this and many now offer AR-15s with a mid-length option.
Recommendation: Any popular gas system length will work. However, as I stated throughout, the gas system length has a significant impact on the way your weapon will perform. Understand fully the relationship between barrel length, gas system length, and dwell time before you make a purchase. Generally speaking, a shorter gas system will run harsher than a longer one due to the difference in port pressure. I find that a mid-length gas system is a really good length even on typical carbine length barrels.
Bolt Carrier Group
This is the last major component of the upper receiver that I’ll talk about. But it’s right up there in importance with the barrel, and, incidentally, a lot of the considerations are the same. So, much of what I’ll discuss here will be familiar.
The bolt carrier group is actually a combination of a few parts, the most important being the bolt, bolt carrier, and firing pin.
The bolt itself is responsible for extracting spent rounds and locking new rounds into battery. In addition, it has a small hole that allows the firing pin to strike the primer when you pull the trigger.
The bolt fits inside the bolt carrier and is held in place with a cam pin, which allows the bolt to rotate slightly as it cycles.
The bolt carrier is the largest portion, and, besides housing the bolt, serves two main functions. First, it has a gas key bolted to the top, which docks with the gas tube.
As discussed in the previous section, a small amount of hot gas is siphoned through the gas system to the gas key and the energy pushes the bolt carrier group rearward allowing the old round to be ejected and a new one to be fed.
Second, the bolt carrier resets the trigger so that you may fire another round. In the case of a fully automatic weapon, the bolt carrier will also reset the auto sear.
Together, these components undergo a ton of stress, which necessitates the use of sufficiently durable materials, high-quality finishes, and proper testing.
These measures go a long way toward ensuring your weapon is reliable and long-lived. Manufacturers know this and will go out of their way to give all the pertinent specifications. If they don’t, well, that’s a good sign you should walk away.
Before I get too long-winded, let’s dive into a few of the most important considerations you need to keep in mind when researching an AR-15 bolt carrier group.
Bolt Carrier Group Materials
When it comes to bolt carrier group materials, there are a lot of options. That includes some exotic materials like titanium, which are becoming quite popular.
Though, when we talk about an off-the-shelf AR-15, carbon steel is the most common construction material. In the interest of time, that’s what I’ll cover here. Specifically, I’ll discuss grades 8620, 9310, and Carpenter 158 steel, which are by far the most prevalent.
Much like the barrel materials mentioned above, these grades are exceptionally durable and suit this application well. These materials are also readily available and easily machined, which means you get a better product at a lower price.
To expand on this a bit more, I’ve broken down these specific materials below. I’ll outline their benefits and where they best fit in.
9310 Steel
This is a nickel-chrome-molybdenum case-hardening steel, with good strength and toughness properties. It shows high hardenability, high core hardness, and high fatigue strength. It’s also replacing Carpenter 158 and 8620 steel in a lot of cases.
9310 steel exhibits significantly higher tensile and yield strength than 8620 steel, making it an excellent choice for bolt carrier construction. In addition, it can be cased hardened and is comparable in strength to Carpenter 158 steel, making it an equally good choice for bolt construction.
A lot of manufacturers are moving towards a completely 9310 steel bolt carrier group or at least have the option. Though this is a relatively new phenomenon and that makes some people nervous. Many prefer the tried-and-true 8620 and Carpenter 158 combination rather than the 9310 option. In my opinion, both are perfectly acceptable.
8620 Steel
This is the most common material used for bolt carrier construction and it works very well. So well, in fact, that it is specified by the US military for all M4, M16, and variants.
It is a bit softer and less strong than the 9310 option, but that’s fine for this application. A properly machined and tested bolt carrier made from 8620 steel will last a lifetime in most cases. It is certainly up to the task as evidenced by the millions in use already.
Carpenter 158 Steel
This a very common material for use in bolt construction, and, like 8620 it is the choice for military applications.
Carpenter 158 steel is actually a proprietary alloy made by a company named Carpenter Technology Corporation. It is renown for having a very high core strength and hardness. In addition, it has excellent wear resistance traits that allow it to withstand severe abrasion, where softer materials may falter.
Because of these characteristics, Carpenter 158 is the standard by which other bolt materials are measured. A precisely machined and tested part is exceedingly tough and reliable.
Recommendation: This goes without saying, but I like to stick with what works. When it comes to bolt carrier group materials, 9310, 8620, and Carpenter 158 steel just work. Along with selecting the right material, keep in mind who the manufacturer is. A reputable manufacturer generally has access to the best materials and machining capabilities. Proper finishes, linings, and testing are important, too. So keep that in mind as you continue in this section.
Bolt Carrier Group Finishes & Linings
The overall purpose of any finish or lining is to protect the material from abrasion and corrosion. They also add lubricity, make things easier to clean and keep your weapon running smoothly and reliably.
In general, the bolt carrier group will have a durable outside coating and a similarly tough lining. Milspec bolt carrier groups, for example, will have a phosphate finish and chrome lining.
Some finishes, like nitride or nickel boron, are used as both a finish and lining. These finishes, in particular, are exceptionally durable and very slick, making them viable for both applications.
The tough part is determining which finish and lining are right for you. Since there are so many available options, things can get confounded pretty fast. To add to the confusion, some manufacturers may use names for an already established process that’s widely used by the firearms industry.
Suffice it to say, though, a high-quality finish and lining is essential. To what extent will depend on your application. Meaning exotic finishes may not be necessary if you’re AR-15 is just a range toy or home defense weapon, so really keep in mind the intended application.
With that said, I’ve outlined a few common finishes and linings below. This isn’t an all-inclusive list, but it should clear some things up.
Chrome
Chrome is an exceptionally hard and slick material, commonly used as a lining for bolt carrier groups and gas keys. It’s also a common lining for barrels, as I mentioned before.
Another key characteristic of chrome is its ability to withstand heat. This is necessary because hot gas siphoned through the gas system is vented directly into the bolt carrier group. Without sufficient treatment, the metal itself tends to erode over time.
Because of its durability, some manufacturers even use it as a finish for their bolt carrier groups. The relatively non-porous surface also makes clean up easy and reduces the need for additional lubrication.
Phosphate
Phosphate is popular because it is cheap and simple to apply, yet provides good corrosion protection and improved friction properties of sliding components like the bolt carrier group.
Most off-the-shelf AR-15s will have have a phosphate finished bolt carrier group. Other coatings typically demand a premium. However, this is a very capable finish and suits most applications.
Nitride
Nitride is becoming very popular, and for good reason. Like phosphate, it is relatively cheap and easy to apply but offers a significantly higher level of protection. It is also very slick, so you won’t need as much lubrication and it’s very easy to clean.
The nitride process actually impinges nitrogen into the steel itself, effectively case hardening it. It can also be used on a number of other metals and is used as a barrel finish and lining, too.
Nickel Boron
The is another very popular finish and lining. Like nitride, it offers a significantly higher level of protection when compared to phosphate. It’s also very slick, reducing the need for additional lubrication and cleaning.
Nickel boron plating is an auto-catalytic coating process that deposits nickel onto the steel. Unlike the phosphate and nitride process, it isn’t necessary to pass an electric current through the solution to form a deposit
Nickel boron coatings are columnar in growth, resulting in a distinct nodular topography which serves to reduce surface-to-surface contact of two sliding surfaces reducing drag and friction.
The nodular structure also dissipates heat at greater efficiency due to a greater surface area, making this an excellent choice for firearms applications.
Recommendation: The new and exotics finish work great, but so does phosphate and chrome. In most cases going with something else is not necessary, rather it’s a matter of preference. When it comes to off-the-shelf AR-15s phosphate and chrome are your most common options. If you want something different, you will need to purchase it separately or step up into a higher end model.
Bolt Carrier Group Testing & Inspection
This is probably your most important consideration when you talk about a bolt carrier group. Without proper high-pressure and magnetic particle inspection, your risk of getting a compromised part is greatly increased.
For the most part, reputable manufacturers thoroughly test and inspect their product to ensure maximum reliability. Others may forego these processes as a means of cutting cost, in which case I would pass.
The idea behind high-pressure testing and magnetic particle inspection is the same as for barrels. High-pressure testing involves exposing the bolt and bolt carrier to stress as a means of determining if the material meets or exceeds the standard.
Magnetic particle inspection is a means for identifying near surface defects that may lead to premature failure. The process involves inserting the part between two poles of an electromagnet and saturating it with a suspension of magnetic particles. An ultraviolet light is then used to inspect the surface looking for visible cracks or other defects.
Recommendation: A combination of things go into making a great AR-15 bolt carrier group. Good materials, finishes, linings, and testing are essential. My final recommendation is to choose an AR-15 from a reputable manufacturer. Doing this goes a long way toward determining the quality of all parts, not just the bolt carrier group. These guys thoroughly test and inspect their parts as a means of quality control and it shows because they continue to build a strong reputation.
Lower Receiver
Finally, we get to talk about the other half of the AR-15. The lower receiver has a number of important features, which we’ll talk about in depth below. It houses the trigger group, trigger guard, magazine release, selector switch, and bolt catch. It is threaded on one end to accept the buffer tube, buffer, and spring. Finally, it has provisions for a pistol grip.
Just like the upper receiver, in this context, it is referred to as a “stripped” lower receiver. But in the case of a complete rifle, the lower receiver will be fully assembled and include the components mentioned above – this is called a “complete” lower receiver.
Also like upper receivers, there are two types of stripped lower receivers – forged and billet. Forged receivers are by far the most popular, offering superior strength and value.
Billet receivers, while not as popular, offer more aesthetic and performance tweaks than a comparable forged part. Though, they’re not as strong in most cases and tend to be more expensive. But they are more than capable in this instance, so don’t let the strength and price deter you if you want a billet receiver.
In general, lower receivers are made from 6061-T6 or 7075-T6 aluminum alloy. For this application, 7075-T6 is the preferred material since it is stronger than 6061-T6 in every way. And, just as important, the price for the superior 7075-T6 aluminum is very close to 6061-T6.
The lower receiver has the same finish as the upper receiver – usually hard coat anodizing. Hard coat anodizing provides a good level of protection against corrosion and abrasions. It even adds a level of hardness to the metal beyond what other finishes may provide.
Other high-quality finishes are available, too. Cerakote and Duracote are very popular and let you chose other color options besides the standard black.
Recommendation: Look for a lower receiver that is made from 7075-T6 aluminum. While 6061-T6 is acceptable for this application, 7075-T6 offers better value when you consider it’s superior durability. Which type of receiver you select (forged or billet) is a matter of preference, but understand the pros and cons of both. Most off-the-shelf AR-15s will have a forged upper and lower receiver. If you are looking for a billet receiver, you likely pay a considerable premium. Finally, the receiver should have a high-quality, durable finish – hard coat anodizing or better.
Lower Receiver Parts
The list of parts for the lower receiver is long. Thankfully, that list mostly consists of roll pins and springs. The major components are the trigger group, bolt catch, magazine catch, takedown and pivot pins, pistol grip, and associated parts.
Like the upper receiver parts, there shouldn’t be any functional difference between manufacturers. They are pretty standard across the board, which lets you mix and match parts from different companies without issue. There may be differences in aesthetics, however, and some lower receivers require proprietary parts depending on the situation.
The key thing to consider is who makes the parts. Purchasing your parts from a reputable dealer is the best way to ensure they are good quality. However, since you are looking to purchase a complete AR-15, this is a relatively minor consideration.
Quality parts will be properly machined and finished to standard. This ensures that things fit properly and function reliably. Like everything else, finishes are important because they protect against normal corrosion and abrasion.
Recommendation: To reiterate, choosing a reputable company for your AR-15 is one of the only ways to guarantee good parts. These manufacturers produce quality goods, which is why they have such a strong reputation. Aesthetic choices are totally subjective, so choose what you want as long as it fits the guidelines I mentioned.
AR-15 Triggers
The standard AR-15 trigger group consists of a trigger, disconnector, hammer, and a complement of springs and pins to hold everything together.
The way it operates is pretty straightforward, however explaining it is a bit tricky, so bear with me. Essentially, the trigger portion interfaces with the spring loaded hammer. When you pull the trigger the connection is broken and the hammer swings up to hit the firing pin.
After the round is spent, the energy from the gas system pushes the bolt carrier group rearward. Simultaneously, the bolt carrier pushes the hammer down where it catches on the disconnector, allowing the action to cycle unimpeded. When you release the trigger, the disconnector unhooks and the hammer reengages the trigger ready to be fired again.
Other two stage and match triggers are available as well. These triggers offer slightly different functionality with the purpose of reducing the amount of pressure needed to actuate the trigger. These triggers are constructed and operate differently depending on the manufacturer, so it isn’t feasible for me to describe how they work here.
However, in most cases, the initial stage of a two-stage trigger takes a lot of the engagement between the trigger and hammer out of the equation. This means you need less pressure to actuate the hammer, which happens in the second stage. The result is a smoother, lighter trigger overall.
When we consider triggers, most budget and mid-range AR-15s will have a standard one stage mil-spec type trigger. For more improved triggers, you will generally have to step up in price.
The standard mil-spec trigger is very reliable, if not the smoothest and lightest. Some people even prefer a single stage trigger because of the reliability and positive break and reset.
Some companies try to improve on the trigger itself by polishing the surfaces that contact each other. They may also add a finish like nickel boron or chrome that lets the pieces slide off one another more efficiently. This is actually an upgrade that some offer on their budget and mid-range guns.
Recommendation: Most budget and mid-range AR-15s will come with a standard, or slightly improved mil-spec style trigger. These triggers are very simple and dead reliable, which makes them a perfectly acceptable choice for most people. By their nature, they are heavy, sometimes gritty, triggers but they have a very positive break and reset points which are sometimes preferable. Two-stage and other aftermarket triggers are made to be light and smooth. This is beneficial, especially for competition and distance shooting, because it makes the weapon more accurate in a practical sense. Overall, if you want an upgraded trigger you will need to spend the extra money.
AR-15 Accesories
Accessories and furniture are the last pieces of the puzzle. What you choose will have a significant impact on aesthetics, comfort, and performance. As such, it’s important to know your options and understand what you should be on the lookout for.
I’ll break down the furniture first, specifically handguards, buttstocks, and pistol grips. Then I’ll move on to backup iron sights and optics.
What furniture you get will largely depend on your budget. For example, most budget, and even some mid-range options come with the standard mil-spec style furniture. That includes polymer drop-in handguards, collapsible buttstocks, and A2 style pistol grips.
As you move up in price, you start to see proprietary or aftermarket equipment that is better looking with improved quality and performance.
Though, one thing that sets the AR-15 platform apart from a lot of others is its modular design. That means you can change and upgrade parts very easily. So, over time, if you are not satisfied with something you can just replace it. The aftermarket support is phenomenal.
Same goes for other accessories like backup iron sights and optics. The standard fare works well, but if you want to step up your game you will need to step up in price, too. Optics, in particular, can reach astronomical prices in some cases.
To explore this a bit further, I’ve broken things out separately. That way you can get a good understanding of your available options, regardless of your budget. This is also a useful section if you plan on upgrading in the future.
Recommendation: There are seemingly unlimited options as far as accessories and furniture are concerned. When it comes to off-the-shelf AR-15s, however, you’re usually limited by your budget. If you want something beyond standard mil-spec fare, you will pay more. Nonetheless, all accessories should be of sufficient quality. In this case, that means accurate machining and finishes which ensure proper reliability and fit.
Handguards
AR-15 handguards are generally made of two materials – polymer or aluminum. Other materials are available, but are not as common and won’t be mentioned here.
Handguards provide an area at the front of the weapon to grip so that you can effectively maneuver and aim your weapon. They also provide protection from the barrel, which becomes very hot after only a few rounds. Finally, the handguard provides a means for mounting accessories like sights, grips, and lights.
The key to choosing the best handguard is to keep all of these things in mind. For example, if you only use your weapon at the range or as a personal defense weapon, attaching accessories may not be a priority. In which case, a standard drop-in handguard will suffice.
Before moving forward, I think it’s pertinent to identify the two types of handguards first – drop-in and free float handguards.
Drop-in handguards have two pieces that fit together around the barrel. The two pieces are held in place by a cap at the top and the delta ring assembly at the bottom. They are usually made from polymer, but aluminum drop-in handguards are available, too.
These types of handguards are used because they are simple and cost effective. However, since they interact with the barrel itself, it can degrade accuracy to a very small extent. It will be undetectable to most shooters, but if ultimate accuracy important to you then a free float handguard may suit you better. Understand, though, that this will be paying more in most cases.
Free float handguards don’t interact with the barrel in the same way as drop-ins and are generally considered more accurate. They are one solid piece and slip around the barrel from the top and are attached via the barrel nut. They’re almost always machined from aluminum.
Besides selecting between drop-in and free float, you will need to consider accessory mounting standards – the most common of which are Picatinny, M-LOK, and Keymod. Others are available, but they are not as prevalent. Some handguards, like those found on budget models, have no way to mount accessories at all.
The Picatinny rail provides a standard mounting platform that is extremely durable and holds everything in place very securely. The rail itself consists of multiple transverse slots similar to the old Weaver rail mounts. This is the standard mounting standard used by the military, and a lot of free float handguards have a Picatinny rail on top to mount sights and optics.
M-LOK and Keymod are relatively recent additions that are really starting to gain traction in the AR-15 community. They provide an effective way to mount accessories without the bulk associated with Picatinny or quad rails. They offer improved comfort, aesthetics, and are very secure. Both standards are very capable and there’s no real clear winner here.
Recommendation: Which handguard you choose will largely come down to preference and budget. Lower price AR-15s usually come standard with polymer drop-in type handguards, while more expensive models may come with free float handguards with M-LOK or Keymod rails. My preference is for free float handguards because of their improved performance and versatility. However, any handguard will suffice and they are easily changed down the line if you choose.
Buttstocks
Buttstocks come in a variety of flavors and there are endless choices. To keep things simple, I’ll outline your basic options rather than get too far into the weeds. As a general rule, there are two types of buttstocks – fixed and adjustable.
Fixed buttstocks are static and don’t offer adjustments to the length of pull in most cases. This is an important consideration because the length of pull can affect sight acquisition speed, accuracy, and overall comfort. As such, it’s important to understand what task these stocks are suited for and whether an adjustable stock is better.
Fixed buttstocks are very stable and the best solution for long range and accuracy tasks. Sniper stocks in particular work very well in these situations, and offer a certain level of adjustment to the length of pull and cheek rest height while maintaining the stability inherent in a fixed stock.
Many minimalist buttstocks are also fixed. These stocks are simple and light, making them a great option if you want a featherweight AR-15 or simply like the aesthetic.
Adjustable buttstocks mitigate some of the problems with fixed stocks. While not as stable, an adjustable stock gives you the ability to adjust the length of pull, as well as the overall length of the rifle, on the fly. That’s a pretty big deal for a lot of reasons.
Being able to adjust the stock lets you change the length of pull depending on your shooting style, the shooting style of others, or even the clothes you wear. It’s particularly useful when wearing body armor or a thick jacket where it may be difficult to should the weapon because of the bulk.
Adjusting the length of the weapon makes it easier to maneuver in tight spaces as well. The confined quarters of your house, for example, require a compact weapons system that allows you to rapidly deploy in case of an emergency or home invasion. A fixed stock can make your AR-15 unwieldy in some cases.
Recommendation: Most off-the-shelf AR-15s will come with an adjustable stock in one form or another, with M4-style buttstocks being most common. Fixed stocks are generally relegated to retro-style weapons or ones built specifically for accuracy or other special purpose tasks. However, the benefits of an adjustable stock outweigh those of a fixed stock for most people. As such, it is what I recommend most often.
Pistol Grips
The purpose of a pistol grip is to orient your hand forward allowing you to actuate the trigger and other functions of the weapon. There are more things to consider, however, as the intended use of some pistol grips may not match your needs.
At a minimum, a pistol grip should be well made and free from imperfections that may degrade reliability over time. What pistol grip works best for you, however, is subjective. Preferences for things like texturing, palm swells, and finger grooves differ between each user.
However, most budget and mid-range AR-15s will come with an A2-style pistol grip. This grip is certainly capable and offers a good combination of comfort and reliability. Is it the best? Not by a long shot, but it is fine for personal defense and range weapons.
As you move up in price, other options become available. The aftermarket pistol grips you find on higher-end AR-15s offer improved performance, comfort, aesthetics, and functionality. Improvements in these areas go a long way towards ensuring your weapon functions and fits you well.
Recommendation: Many pistol grip manufacturers offer high-quality, ergonomic, and aesthetically pleasing parts. For the most part, what you choose will come down to personal taste. I would go as far to say that if you stick to a trusted brand, then you really won’t go wrong. For budget and mid-range AR-15s, your rig will usually come with a standard A2-style grip. You’ll need to step up in price if you expect anything different. These parts are cheap and easy to upgrade, however.
Backup Iron Sights
Iron sights let you acquire a target and accurately place a round down range. They’re also important as a backup to your primary optic. Whether it’s a scope or red dot, these types of optics can be fragile and it’s important to have a redundant aiming method in case they are compromised.
When choosing backup iron sights, your two major considerations are durability and accuracy. They should be precisely machined from high-quality materials. This ensures it will stay zeroed even when exposed to abuse.
High-quality iron sights also offer precise adjustment of windage and elevation. The up and down, left and right movement lets you dial in your weapon ensuring maximum accuracy.
Sights are generally made from aluminum or polymer with some steel pieces intermixed. While aluminum is objectively more durable than polymer, real-world testing shows both materials are perfectly capable. In both cases, the sights should match the criteria I mentioned above.
You’ll also want to consider is whether your sights are capable of co-witnessing with your optics. This means you can zero your iron sights and view them through your optic. For magnified optics, offset sights are your best bet.
Recommendation: Many off-the-shelf AR-15s will not come with iron sights. This is to save money and account for the difference in consumer preference. There are a lot of options so conduct due diligence before making a selection. For such an important part I stick with a reputable manufacturer and ensure it has been properly vetted by others.
Where To Buy An AR-15
At this point, you should have all the knowledge you need to select the best AR-15 for your money. The next step is deciding where you want to purchase your weapon from, and I can give some pointers on that.
First things first, though. Make sure you understand the law before making a purchase. Things are different depending on what your local, state and federal laws are. The required identification and paperwork may be different from one place to another, so keep that in mind.
Beyond that, it’s a good idea to shop around before making a purchase. That way you know you are getting the best deal on your AR-15 possible. Here are just some of the ways you can buy an AR-15.
Online
You can buy an AR-15 online, and there are a ton of websites to choose from.
Pros – You get to shop for an AR-15 without leaving your house, you can choose from dozens of sellers, and do research in real time. Since competition is strong and overhead is pretty low for online-only retailers, you can usually find the lowest price available.
Cons – You can’t see and feel your AR-15 before buying. This is a big deal for someone that likes to have something in hand before dropping the cash. However, many reputable retailers understand this and offer a money back guarantee and very lenient return policies.
You will have to pay to ship in some instances, and in all cases, your AR-15 will be shipped to an FFL who may charge you a nominal fee.
Local Gun Store
Supporting local business is important to a lot of people, I included. And a lot of times the experience you find at a gun shop is invaluable.
Pros – You support local business and often get superb customer service. You also get to touch, feel, and experience your AR-15 before making a purchase.
Cons – A lot of gun shops have significant overhead and that usually translates into slightly higher prices overall. That’s not to say you can’t get a great deal.
Gun Shows
Gun shows bring together a lot of retailers in one place, and competition is stiff. That usually translates into big savings for you.
Pros – You get to choose from a number of retailers, and since they are all competing for your business you can usually walk away with a great deal. Some are even willing to negotiate with you – especially if you buy other products or services from them.
Cons – Some bigger gun shows can get packed and the whole experience can be trying at times. There’s not only competition among retailer, but between customers as well. If you’re not quick enough someone else is likely to snatch the deals out from under you.
The Wrap Up
To sum it up, here are the key factors that will help you select the best AR-15:
- Select the right type of upper and lower receiver that fits your application and budget. Forged receivers are great all around and are what I recommend most often. Ensure they made from high-quality materials, are outfitted with solid parts, and are properly finished.
- The barrel should be made with the best materials possible- I recommend 4150 carbon steel, 410 stainless steel, or 416R stainless steel. I prefer a chrome lined or nitride/melonite barrel as it extends the life and performance of the barrel greatly. The barrel should have a high-quality finish to protect against the elements.
- Muzzle devices are an important consideration when choosing an AR-15. But, don’t let it define what you choose, because it’s pretty simple to change out later on down the line. Most budget and mid-range AR-15s come with a standard A2-style flash hider, which is simple and effective.
- Any popular gas system length will work. However, the gas system length has a significant impact on the way your weapon will perform. Understand fully the relationship between barrel length, gas system length, and dwell time before you make a purchase.
- When it comes to bolt carrier group materials, 9310, 8620, and Carpenter 158 steel work well. Along with selecting the right material, your bolt carrier group should be properly tested and have a high-quality finish.
- Most budget and mid-range AR-15s will come with a standard, or slightly improved, mil-spec trigger. These triggers are very simple and dead reliable, which makes them a perfectly acceptable choice for most people. For two-stage and match triggers, you will need to step up your budget.
- There are so many options as far as accessories and furniture are concerned. When it comes to off-the-shelf AR-15s, you’re usually limited by your budget. If you want something beyond standard mil-spec fare, you will pay more.
- Many off-the-shelf AR-15s will not come with iron sights. For such an important part I stick with a reputable manufacturer and ensure it has been properly vetted by others.
This guide is a behemoth (15,000+ words) and it is my sincerest hope that you got all the information you need. As always, I’m available to answer any questions you may have. Drop me a line via the contact page!
![Best AR-15 Gas Blocks: The 13 Best Gas Blocks Reviewed [2024]](https://ar15nerd.com/wp-content/uploads/2017/05/Best-AR-15-Gas-Block-Featured-Image-370x297.png "Best AR-15 Gas Blocks: The 13 Best Gas Blocks Reviewed [2024]")
![14+ Best AR-15 Lower Receivers [Plus Ultimate Buying Guide]](https://ar15nerd.com/wp-content/uploads/2017/01/Best-AR-15-Lower-Receiver-Featured-Image-370x297.png "14+ Best AR-15 Lower Receivers [Plus Ultimate Buying Guide]")
Thank you for the article. Detailed yet easy to understand, and very informative.