The term “AR” derives from the first two letters of ArmaLite Inc, and was originally their classification for the series of rifles spawning the modern variety. Today it generally denotes non-military variants of the M16 family of rifles and carbines, though some specific names are registered trademarks for manufacturers, such as “AR15” and “AR-15” (Colt) and “AR-10” (ArmaLite). This is why we have the somewhat random naming schemes by many different companies making very similar products.
One of the AR’s greatest attributes is its modularity. By my count- and I know I’m missing a few here- at least 33 different chamberings from .22 LR to .50 BMG are possible with the smaller, AR-15 sized receiver. The larger AR-10 sized receiver accommodates at least 9 different cartridges. Changing caliber or configuration is normally just a matter of swapping upper receiver groups. After ensuring the rifle or carbine is clear, a simple pull of the two captive takedown pins in the lower receiver separates it from the upper. The upper receiver group- including barrel, sights, optics, handguards and all- is replaced with a different upper of the same size (small or large), sometimes referred to as a “kit”. Since the lower receiver is classified by BATF as the firearm, uppers can be purchased as a part without requiring an FFL. This affords great flexibility to shooters wanting one firearm with multiple capabilities. Rather than vexing over the age-old “If you could only choose one gun….” dilemma, the choice is made simpler with the AR. The same 24” heavy barreled rifle that performs admirably across prairie dog laden plains can be converted to a handy home defense .40 S&W carbine in about 30 seconds. When big game seasons roll around, that carbine can be transformed into an 18” barreled 6.5 Grendel, providing a wide variety of .256 projectiles to suit various hunting needs. Anyone claiming AR’s aren’t sporting rifles is really missing out on the fun.
The list of each cartridge or configuration changes on a seemingly daily basis, so I’ll simply cover a few of the more popular choices. By far, the majority of ARs on the market are chambered in 5.56x45mm (aka 5.56 NATO), with .308 Win (7.62x51mm) coming in second. In the military, the latter is normally seen in sniper rifle configurations and when built correctly, they’re excellent long range rifles. As consumers become increasingly aware of this platform’s flexibility, firearms and ammunition companies are rapidly responding with more cartridge and configuration options. A notable exception to the normal sized upper/lower configurations is the .50 BMG. Several companies make larger, caliber-unique .50 BMG upper receiver kits. These attach to the existing small lower receivers, functioning as single shot bolt-actions.
For cost effective plinking and small game hunting, complete upper receivers and drop-in conversion units transform a small receiver AR into a .22 LR. Several companies offer adapters for 5.56 receivers that replace the bolt carrier group, chamber and magazine. Although there are other small cartridges for the AR, .22 LR is a great way to plink inexpensively and introduce new shooters to the AR’s excellent ergonomics. Varmint chasers have accurate, high velocity choices in cartridges like .204 Ruger, .222 Remington Magnum and of course, .223 Remington or 5.56x45mm. A word of caution on the latter: though .223 Remington and 5.56x45mm may be dimensionally similar, firing 5.56 in a .223 Rem. chamber may result in dangerous overpressure. It’s safe to fire .223 Rem in a 5.56×45 chamber but the slight differences in chamber dimensions may result in less accuracy due to the increased free-bore or “leade”. An additional chamber is available, normally referenced as a “Wylde” chamber. This is a hybrid of .223 Rem and 5.56 NATO, dimensionally between them. While it handles 5.56 NATO safely, the Wylde is cut slightly smaller to provide better accuracy than a standard 5.56x45mm chamber. Several existing competition records were set with .224 projectiles (the actual diameter of 5.56 and .223 Rem bullets) loaded long for single round, hand cycling. Benchrest shooters have several 6mm options to choose from and the new 6.5 Creedmoor may prove to be a serious 1000 yd competitor.
ARs make excellent predator rifles. Likely options are for coyote and other 4-legged vultures are .222 Remington Magnum, .223 Rem/5.56×45 and .223 WSSM. Bonafide members of the “Buck Fever Club” have many choices in short and long actions. In small receivers we find .25 WSSM, .260 Remington and .300 Rem SAUM. The .300 Whisper is very effective for wildlife management in culling operations with thousands of deer and pigs harvested to date. In the larger action we have .243 Win, .308 Win and .338 Federal as excellent choices for medium to large game. Dangerous game, requiring rapid incapacitation at close ranges, brings out several choices. The smaller action can be built around .450 Bushmaster, .458 SOCOM and .50 Beowulf. While these are all relatively short-range cartridges, they’re reputed to be effective stoppers when mean critters are intent on getting up close and personal.
Shooters with pistol cartridge needs have several popular choices in the small receiver, including 9x19mm, .40 S&W and .45 ACP. In addition to a new barrel and bolt, all require a dedicated magazine and some need a magazine well insert. These chamberings can be handy for close-range use or where pistol cartridge compatibility is important. The longer barrel provides higher velocity over pistols for increased effective range and better potential for expansion of appropriately designed projectiles. The increased sight radius, shoulder stock options, optics and light mounts all serve to enhance accuracy over a pistol.
Form & Function
The AR uses a rotating bolt lock-up driven by one of two basic operating systems: direct gas impingement or operating rod. Direct gas is the most common design and for most purposes works well. In this system gas expands (following the projectile down the barrel), jets through a gas port and tube, directly impinging on the “key” affixed atop the bolt carrier. In barrel lengths of 14.5” and longer, direct gas is very reliable. Shorter barrels (and their shorter gas systems) are prone to reliability problems stemming from high pressure and timing problems. The main drawback to direct gas is that carbon is blown into the upper receiver along with hot gas. The result is a mechanism requiring more maintenance than op-rod systems in order to ensure reliability and a bolt carrier group (BCG) that gets much hotter than in op-rod designs.
Thanks in large part to the H&K 416’s success in the LE/military market, operating rod-driven ARs have received enough attention to appear in the civilian market. Several companies offer either complete rifles or retro-fit kits, but these are expensive and don’t always work on every AR they’re fitted to. Op-rod systems require less gas volume, terminating on either a short-stroke piston or the end of an operating rod that replaces the traditional gas tube and drives the cycle of operation. They tend towards greater reliability in short barrel ARs due in part to a lack of fouling in the upper receiver. Cleaning the BCG and receivers is faster, easier and less frequent. These systems tend to increase weight in the fore-end and the difference can be significant. This has the dual edge of adding more carry weight while mitigating some muzzle rise and felt recoil. Shooters requiring short barrels and/or high-round count and low maintenance reliability of their carbine or rifle stand to gain the greatest benefit from cleaner operating-rod systems.
The need for higher maintenance of direct gas impingement ARs has caused a stir in military circles. In reality, so long as direct gas rifles are maintained properly- all else being equal- they’ll perform when called on. In all my years as both an Infantryman and Special Operations Soldier, provided I took care of my M16s or M4s as much as situations permitted, they took care of me. That’s not to say I didn’t have occasional direct-gas malfunctions, I did. But I also had various types of malfunctions with every other operating system I used, tested or trained with over the years. Direct impingement still works very well for those of us not carrying them in the most demanding environments the world has to offer.
Describing the many faces of AR-style rifles is like trying to keep track of anti-gunners’ schemes to eliminate the Second Amendment. It’s a bit simpler to cover the basic variations. The standard M16A2/AR15 version (right) features a 20” barrel and is distinguishable by its 2-piece hand-guards and fixed carrying handle atop the upper receiver.
The standard carbine is much the same, excepting the collapsible stock and 14.5” (military /LE) or 16” (civilian) barrel (left). These basic AR styles are suitable for general purpose duty, ranch rifles or defensive tools. Variations spring outward from there like the branches of a Carolina pin-oak, covering the spectrum from top to bottom. A very common choice these days in all configurations is the M4-style, or “A3” flat-top upper receiver. Since the carrying handle is seldom used as such, most shooters remove it in favor of a smaller, lighter fixed or flip-up, detachable rear sight. The flat-top also allows lower optics mounting, reducing the need for adding a cheek rest to the stock.
In customizing ARs, free-floating the barrel by exchanging the hand-guards with a free-float tube is a good place to start. This modification eliminates inconsistent barrel pressure, helping potential accuracy while allowing more cooling air to circulate around the barrel. The for-end can be smooth or rail-laden, providing attachment points for accessories. As the quest for greater accuracy continues, stock triggers are easily replaced by drop-in units from several high quality manufacturers. Notable among these are the triggers offered by Geissele Automatics, which are quickly taking the AR market by storm. Geissele’s excellent triggers are currently found in the hands of many competitive marksmen, military and police professionals and are regularly backordered due to their quality and effectiveness. They offer 3 variants for different shooting needs and all make a noticeable difference in downrange performance.
Barrels are another area for improvement. For general purpose defense, ranch-rifle or hunting to moderate ranges (<200 yards), most standard-fare barrels do the trick. Although an occasional stock barrel shoots very well, changing to a match barrel can help shrink group sizes to competitive levels. Standard civilian aftermarket offerings are 16, 20 and 24 inch lengths with a few 18” barrels popping up every now and then. Profiles and weights range from the very thin M16A1 style to heavy bull barrels. A rate of 1:9” is a good general purpose twist for smaller game and lighter/shorter bullets while the harder to find 1:7” and 1:8” twists better serve heavy/long projectile needs. For high round-count shooting, as in heavy plinking or fast-paced competition, chrome lined bores go a long way towards extending barrel life. It’s very difficult to uniformly apply chrome to match tolerances so accuracy purists generally err to non-chrome lined, “chrome-moly” or stainless steel barrels. Swapping barrels isn’t hard but a few specialized tools and mechanical skills are required. It’s important whenever changing barrels that torque and headspace are checked before firing live rounds. Excessive headspace can be a dangerous condition and proper barrel installation is critical for safety so this is an area where using a competent gunsmith is in order if you’re in doubt about your abilities.
The tactical accessory market has boomed in the last few years, allowing AR’s to be accessorized beyond recognition. Picatinney (aka Mil Standard 1913) rail allows the mounting of endless light, optic, bipod, laser and removable iron sight choices. Next to primary sights, the use of a good quality gun-light is the single best accoutrement that a defensive rifle can be fitted with. A gun-light placed for ease of instant use when the rifle is at the ready, aids quick target identification and the use of day sights at close range. Illumination also provides a momentary, disorienting or blinding light source for two and four legged threats. Surefire is the long time industry leader in weapon-mounted lights and continues to stay well ahead of their competitors in both quality and variety.
Their Scout light (above) is an excellent example of efficiency balanced with performance. Shooter installed, two- piece rail systems easily replace standard hand-guards for mounting of lights and sling swivels on non-free floated barrels. Items requiring zero retention, such as lasers, should be mounted on free float rails for rigidity and repeatability. For receivers with permanent carrying handles, shooters on a budget can purchase a rail adapter that mounts into the concave top portion by way of a knurled nut. Though this places optics high, it’s a cost-effective way to make an existing rifle or carbine optics-compatible.
The terms “Pre-Ban” and “Post-Ban” differentiate whether or not the rifle or carbine complies with certain provisions of the ridiculously contrived, 1994 Assault Weapons Ban. This conspicuous piece of legislation was predicated on the belief that specific physical features made a firearm unsuitable for civilian ownership. Unfortunately for gun owners, like most misguided legislation it only served to punish law-abiding citizens who struggled to decipher, understand and comply. Some states and jurisdictions still have laws prohibiting particular features on semi-automatic firearms, including magazine capacity limits. In the case of the AR family, post-ban generally means there’s a fixed stock, no bayonet lug and either a permanently pinned in place muzzle brake or a bare, unthreaded muzzle. Functionally all else is the same with some shooters preferring the non-threaded muzzle for accuracy purposes, particularly in heavy “bull” barrel configurations. Post-ban barrels can be converted to accept a muzzle brake or flash suppressor by a competent gunsmith but with so many pre-ban options available and the relative ease of switching barrels it’s seldom worth the trouble. Now that all previously banned features are legal, post-ban models can be converted to the pre ’94 configuration.
Doughboys returning from WWI forever changed the shape of the US firearms industry by preferring their familiar Springfield’s and captured Mausers to the lever-action rifles that dominated the late 19th century. At least three generations of US military men and women have carried some variant of the M16 as their basic rifle. It’s taken a long time for this durable design to move into mainstream shooting activities, hunting in particular. I’m pretty sure there was plenty of griping amongst my great-great-grandfathers’ generation as their old Winchesters, Marlins and Savages were relegated to deer camp duty. While AR’s don’t possess any earth-shattering new technology, they do offer high quality, accurizable, endlessly customizable rifles and carbines in calibers across the spectrum. I’m not the smartest guy sending rounds downrange but I believe the AR will be a useful tool for the citizens of this great nation for generations to come. That is, as long as we ensure politicians who support our Second Amendment-guaranteed rights are elected. If you value the ability to choose your tools for self defense, hunting or sporting use, educate yourself about where your political representatives and candidates truly stand on this right and always vote to preserve the freedom so dearly won and graciously handed to you as a citizen of this great country.