What to Look for When Buying an AR-15

Over the past 60 years, the AR-15 has become “America’s rifle” and grown exponentially in popularity. Here is how to pick a good one.

Purpose

First, as the AR platform is perhaps one of the most modular firearms in history, these guns are available in formats to appeal to a wide array of users. Choose a gun that fits your needs. If you are looking for a hunting arm, there are several ARs built specifically to fit that market in calibers such as 6.5 Grendel, 6mm ARC, and .300 Blackout. For those looking for a target shooter, heavy-barreled guns with 20-inch barrels abound. A good general-purpose sporter? Look for something more like a $600 entry-level S&W M&P15 or Ruger AR 556 with a 16-inch barrel and M4-style stock. Some people collect PEZ dispensers and pay more than that. Want something more compact? AR pistols can fit that bill.

Brands

One top thing to avoid when it comes to buying an AR-15 is to steer clear of unsolicited advice that is arbitrary when it comes to brand names. For example, Armalite designed the rifle in the late 1950s and sold all the rights to Colt, who was the leading producer of these guns in both select-fire and semi-auto formats for more than two decades. Does this mean that Colt’s AR-15s are the pinnacle of AR-15 development? Not necessarily. Likewise, do not turn an inexperienced nose up at a so-called “bottom shelf” AR brand just because owning one would be something “the poors” do.

When it comes to choosing these guns, the components, how they are mated together, and how the company stands behind their work is everything. So, let us get into that.

Barrel length and type

It is not rocket science, the longer the barrel on a firearm the chances are higher that a cartridge will have more complete propellant burn and impart the maximum velocity to the bullet. In short, longer barrels wring more performance. This has been extensively tested by a number of big brain guys in the firearms industry when it comes to 5.56 NATO-caliber firearms and it seems like there are somewhat diminishing returns in barrels longer than 24-inches and a nosedive in ballistics in those below 14.5-inches in length. As such, splitting the difference with a 16-to-18-inch barrel is something of a sweet spot for 5.56 with the 20s providing a good length for those who are aiming for more of a target rifle.

Barrel profile is also a subject that is up for debate for the rifle’s purpose, with lighter “pencil” barrels offering decent practical accuracy while keeping the gun light, and heavier profile barrels better geared for work at a distance. Most common ARs on the commercial market today have barrels made of 4140 chrome-moly steel– which most users will never put enough rounds through to shoot out– while those advertised as being “mil-spec” will typically be made of stronger MIL-B-11595-E chrome-moly or 4150 steel. Target-style barrels will usually be of 416/410 stainless. Chrome lined or nitrided barrels will last longer.

This all brings us to…

Twist rate?

Any rifled barrel has a “twist rate” which is simply a way to determine the degree of spin imparted on a projectile that passes through it. Measured typically in inches, a 1-in-7 twist rate just means that the rifling will spin a bullet fired through it one complete revolution every seven inches. Relax, there isn’t a test on this later, just keep in mind that lighter bullets work better on a looser twist while heavier bullets perform better on tighter barrels with faster rifling.

For example, when it comes to AR-15s firing 5.56 NATO rounds, a heavy 77-grain bullet would perform better in a gun with a 1-in-7 twist and be less than optimal in one with a 1-in-12 twist rate. Likewise, light bullets, such as a 55-grain load, works great in a slower twist rifle such as a 1-in-12 but starts declining in performance in a tighter barrel such as a 1-in-7. All of this goes back to satisfying the purpose you are buying the AR for and then matching your ammunition selection to your gun of choice.

Lower and Upper construction

Keeping in mind that the AR-15 came originally from a gunmaker that was a subsidiary of an aerospace company, it should surprise no one that the upper and lower receivers of the rifle were made from aluminum, typically billed by makers as being “aircraft grade.” In a nutshell, 6061 aluminum is less expensive while 7075 is stronger. Likewise, buyers will also see receivers listed as being either “forged” or “billet,” meaning they are either produced by hammering two receiver halves together or milling one from a single piece of aluminum, with each having their fans.

Almost all ARs these days have M4 feed ramps, which is something you want.

Polymer AR lowers have also been in circulation for years, with mixed reviews when compared to aluminum lowers, especially for heavy use in centerfire guns.

BCG

No, this doesn’t have anything to do with glasses. The bolt carrier group, or BCG, of an AR platform does a lot of the heavy lifting when it comes to how it performs. Heavier mil-spec BCGs, sometimes listed as “full-auto” although they do not violate NFA rules when used in a semi-auto AR, can help provide better lock time and reduce wear and tear as they have more mass. Lighter competition bolts also have their place.

The construction of a BCG will range across alloys from 8620 steel, to 9310 and Carpenter 158 steel, and finally to S7 tool steel with tensile and yield strength increasing– along with cost– across that range. Does that mean that 8620 is junk? Not by any means as it is typically seen as being mil-spec for bolt carriers. When used in a bolt itself will 8620 hold up as long as a C158 bolt? Probably not. Keep in mind that the tougher the steel used means the longer the BCG will last, and the BCG is a typical failure point on an AR once you get past a thousand rounds.

Added to this are “enhanced” bolts that use more exotic coatings like DLC, titanium nitride, chrome, and nickel boron with updated profiles. This contrasts with most standard bolts that have a dull black manganese phosphate coating. More than just being pretty, enhanced bolts are more on the high-performance end.

To make sure a BCG is thoroughly tested, check to see if the bolt itself is shot-peened for surface strength, high pressure tested for shock resistance, and magnetic particle inspected for integrity– processes typically listed as SP, HPT, and MPI. Further, gas keys should use grade 8 screws (not “YFS” screws) that are properly staked.

Rails

Throughout most of the existence of the AR-15, the platform came standard with a two-piece A1 or A2 style plastic handguard, with and without a heat shield strip on the inside, that didn’t allow for much in the way of customization or support for accessories like lights and bipods. While this old -school style of handguard is still popular with DCM rifles for competition or those seeking an increasingly popular “retro” look, ARs these days are typically offered with a free-floating accessory rail that provides for adding everything under the sun.

While KeyMod mounting systems had the early jump in this field, they have been losing ground to Magpul’s M-LOK system which has become the de facto standard, even in the military.

Speaking of rails, ever since FN produced the M16A4 for the Marines in 1987 with a removable handle and full-length M1913 Picatinny top rail for optics and back-up iron sights, such a format has become the benchmark for ARs except for throwback builds.

Triggers

Unless buying a high-end AR, most commercial guns on the market today are offered with a “standard” or “mil-spec” trigger which generally breaks in the range of 5.5-to-8.5 pounds. For seasoned users, these triggers are often described as “heavy” with a good bit of creep. However, they are a good baseline for ARs, which is probably the reason why gunmakers put them on their entry-level offerings. Should you want something better and more responsive, there are seemingly dozens of aftermarket trigger makers including CMC, Geiselle, Rise Armament, Timney, and others that cut the pull weight down to as low as 2-pounds while offering a much crisper break.

In closing

With all that in mind, sit down and look at what you want from your prospective AR, then identify those attributes and begin your search for a platform– be it a rifle, carbine or pistol– that best suits those needs. A little homework will help you with that selection and save you from either under- or over-buying. With so many options out there these days, there is no reason why you shouldn’t be able to find something that checks the boxes and is still tough enough to get it done.

Then again, you can always explore AKs.

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