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Published in Guns & Ammo's 2007 Book of the AR-15

The ArmaLite Infantry Rifle is intended for sporting, defense, and law-enforcement use.
Does the 20-inch A2 rifle have merit amid the trend of optics and shorter carbines, such as the M4 and CQBR? With one of ArmaLite's M15A2 Infantry Rifles in hand, I endeavored to find out.

No compendium of the AR-15 would be complete without ArmaLite, which was first established as a division of Fairchild Engine and Airplane Corporation in 1954. Eugene Stoner, a WWII Marine with expertise in ordnance, became ArmaLite's Chief Engineer and designed the AR-10 and later the AR-15. When Fairchild hit hard times in 1961, it sold the AR-15 patents to Colt's Manufacturing and sold the

The Infantry Rifle exhibited good fit and finish, with a snug upper to lower fit which could still be broken down without a punch.
division as ArmaLite Incorporated. Stoner himself left to be a consultant to Colt's in 1961.

With the patents to the original Stoner rifles out of reach, ArmaLite Inc. designed the AR-18 rifle around a gas piston operating system on a sheet-metal receiver. Due to bad timing and teething problems of the new design, the AR-18 was not able to displace the M-16. The rifle suffered a similar fate when shopped to the UK's Ministry of Defense. With the AR-18 a

The author's first test of the ArmaLite Infantry Rifle after zeroing was a practical action-rifle match.
flop, ArmaLite was sold to Elisco Tool in 1983, who didn't add much to the story.

Meanwhile, Lewis Machine & Tool Company (LMT) had been manufacturing AR-15 and M16 parts. In 1986, Karl Lewis and Jim Glazier formed Eagle Arms to serve the retail business that had been distracting LMT from manufacturing parts. With the Stoner patents expired, Eagle started producing complete AR-15 pattern rifles in 1989.

In 1994, Mark Westrom bought Eagle Arms. Westrom had been an Army Ordnance

The conventional-looking M15A2 conceals the improved bolt and ArmaLite's Tactical Two-Stage Trigger.
officer, an employee at the Weapons Systems Management Directorate of the Army Armament, Munitions, and Chemical Command (AMCCOM) at Rock Island Arsenal, and a Service Rifle competitor. Through a circuitous path of introductions, Westrom met John Ugarte, who had been the last President of ArmaLite at Elisco tool and retained the rights to the ArmaLite name. In 1995, Westrom secured the rights from Ugarte and ArmaLite was back in business, shipping rifles by the end of the year. In the following ten years, the new ArmaLite shipped more rifles than ArmaLite did total prior to 1987.

Much like the ArmaLite of Stoner's era, Westrom's ArmaLite is a leader in

Though the M15A2 lacks a free-float hand-guard, the author didn't find deflection of the medium-contour barrel to be a problem on practical targets.
innovation. As one of the largest manufacturers of AR-15 rifles and parts, it has the R&D resources available for engineering studies required to redesign parts and bring improvements to the overall rifle design. For example, the mid-length gas system which has become popular in the last few years was first offered by ArmaLite to help avoid extraction problems with the 7.5-inch carbine gas system. The rifle I sampled hosted a few other changes only a detailed examination would reveal.

Popping open the hard-case containing the ArmaLite M15A2 Infantry Rifle, I was

The new adjustable ArmaLite two-stage trigger (center) differs from the Rock River National Match trigger (left) and a stock single-stage trigger (right).
greeted by what appeared to be a standard A2 rifle, two 3-round magazines, a web sling, a chamber flag, and the M15A2 Operators Manual.

The rifle is built around a 20-inch chrome-lined carbon steel barrel. Its profile under the hand-guards is 0.90 inch and it is heavier than the standard A2 (0.605 to 0.675 inch). Likewise, the profile is lighter than the common 1.0-inch thickness of National Match barrels. The barrel is cut with a standard 5.56 NATO chamber that can safely fire military 5.56 mm ammunition and enhances

There is no wear on the deprecated lug on ArmaLite's improved bolt (left), compared to a standard Colt's bolt (right).
reliability compared to tight match chambers.

The front sight assembly provides a sling mount, bayonet lug, and front sight post width of 0.075 inch. Staying with the simple theme, the rifle has standard two-piece hand-guards with heat shields.

The upper receiver has a fixed carry handle with A2-style sights. Because most people find it easier to shoot accurately with the smaller aperture, ArmaLite uses a small hole on both the short-range and long-range apertures. The A2 fixed stock provides a length of pull of 13.5 inches.

ArmaLite has snuck several new changes into this rifle, which otherwise looks like a bone-stock A2. The first is a new trigger design, called the Tactical Two-Stage Trigger. With concerns over lawsuits, many law-enforcement rifle users can not use match triggers. The new Tactical Two-Stage Trigger provides a

The lug opposite the extractor on ArmaLite's improved bolt is about 0.02 inch shorter than the rest to better balance recoil forces on all the bolt lugs.
good two-stage pull which can be mechanically configured by an armorer to weights between about five pounds for match use and seven pounds for police use.

Like any machine, the AR-15 has some parts that will eventually wear out. The bolt is one of these, contributing to both infant mortality failures and long-term failures for bolts with over 10,000 rounds. These failures usually involve cracks developing at the base of the two lugs adjacent to the extractor or at the cam pin hole causing the bolt to eventually break.

The AR-15 bolt can be thought of as starting with eight lugs around its circumference. One is cut away to provide room for the extractor. During firing, this asymmetry causes the bolt to warp slightly due to uneven support and put approximately 80% of the force load on the two lugs adjacent to the extractor. It's no surprise that the majority of bolt lug failures occur at one of these two lugs. ArmaLite's solution is to balance the force by only using

six of the seven lugs for load-bearing, restoring symmetry under load. This change is accomplished by simply shortening the back of the lug opposite the extractor so it does not engage the barrel extension. ArmaLite's engineering study determined that this change alone reduces the stress on the two problem lugs by about 40%.

Besides sporting use, the M15A2 Infantry Rifle is intended to be used by security customers such as law-enforcement. I set out to test it in some practical exercises. There are two places where you can consistently see firearms fail and hear their owners say, "I don't understand, it worked great

The long sight radius of the 20-inch rifle aids aiming, especially when engaging distant targets.
when I shot it last weekend." The first is a training class, and the second is a practical shooting match.

I am lucky to live in a part of the country with a dedicated community of practical shooters: USPSA/IPSC, three-gun, and action rifle. In particular, the monthly Pueblo Rifle Match is run by an experienced Law Enforcement Officer who believes rifles should be used to their full capability. In other words, it's a hard match, with targets from contact distance to 425 yards.

With the sights zeroed at 50 yards, the 20-inch A2 shooting 55-grain mil-spec ammunition has a point-blank distance of about 300 yards.
The most common setup for this match is an 16 to 18-inch AR-15, with a low-power optic such as the Trijicon ACOG, Accupoint, or Schmidt & Bender Short Dot. These optics aid target location, acquisition, and sight picture, especially for small targets, distant targets, and targets that have very low contrast with the background. I was curious to find out how this stock A2 rifle would fare, and how much more difficulty I would have with the iron sights compared to a modern optic.

The first order of business was to get the rifle zeroed. Since adjusting the

From a stable position, LaRue targets at 400 yards can be hit using just over a foot of Kentucky elevation.
elevation knob of the A2 rear sight is a no-go under stress and on the clock, I used a 50-yard zero. Shooting 55-grain Federal XM193, this trajectory puts the point of impact 1.7 inches high at 100 yards. It has a maximum height of 2.5 inches at 160 yards and is back to line of sight at about 260 yards. At 300 yards, it's three inches low and at 400 yards, it's 13 inches lower than the line of sight. In summary for targets eight inches tall, I could hold dead on from point blank out to about 300 yards and just remember to hold about a foot high at 400 yards. This kind of zero setup takes advantage of the long point-blank distance of the 5.56 cartridge, and shooting the fast M193-spec ammunition from a full 20-inch barrel doesn't hurt. Accuracy testing showed the

Shown here an instant before ejecting an empty case, the M15A2 ran reliably from the box, with no break-in or additional lube.
rifle will shoot one to two inch groups at 100 yards with 55-grain mil-spec ammunition.

The format at the Pueblo Rifle Match is three or four separate stages, each of which has between five and eight shoot positions spread around the berm with a total of about 30 target opportunities. Targets can be pretty difficult, and running 75 yards before trying to engage an eight-inch circle at 350 yards from an improvised position doesn't make it any easier. It's not uncommon for shooters to go through four or five magazines due to the time pressure and difficulty. Needless to say, guns get really hot and any failures that can happen usually do.

With only about 20 rounds fired during zeroing and no additional lube added, the rifle operated perfectly during the course of the match. I lent the rifle to another competitor whose rifle was constantly malfunctioning and it ran well for him also.

For shooters used to carbine and mid-length gas systems common on 16-inch and shorter AR uppers, the full 20-inch A2 with its rifle gas system has a smoother and more mild recoil impulse. Compared to a carbine gas system, the rifle-length gas tube gives more dwell time before the bolt starts to unlock, the chamber pressure is lower, and the gas vented through the gas port is lower pressure.

With optics almost ubiquitous on fighting rifles nowadays, it's easy to under-estimate what is possible with iron sights. At the Pueblo Rifle Match, I had no problems hitting the 400-yard LaRue and popper targets from steady

The small close-range aperture on the Infantry Rifle can slow target acquisition for close-range targets and limit visibility.
positions. I did, however, have trouble engaging small targets at intermediate range which had low contrast with the background. It was simply too hard to visually make out the target, whereas a low-power optic could easily resolve the sight picture. At close range, iron sights have a slight speed disadvantage to one power red dot sights like the Aimpoint M3.

I have only a few criticisms of the M15A2. The small size of the close-range aperture on the rear sight is a liability for low light or fast target acquisition at the fighting distances the M15A2 is likely to be employed. While most shooters may like the small aperture for target shooting, the A2 sight already has a small aperture which can be used for that purpose. Likewise, the A2 sight is more complicated than needed for a basic patrol rifle. For most

After a thorough wringing-out in mud, snow, and sand, the ArmaLite did not disappoint.
shooters, the five eighths-inch shorter M16A1 stock fits better than the A2 stock. The 20-inch barrel and long fixed stock are liabilities when operating in buildings or vehicles.

With a lot of modern AR-15s decked out in free-float rails, optics, lights, fore-grips, the M15A2 might look a little out of place. It's easy to get caught up in the arms race of the latest gear and forget that a simple rifle, built right, can get the job done. The M15A2 should not be underestimated.

The M16A2 Sight
The A2 rear sight replaced the M16A1's much simpler design when the M16A2 was introduced in 1985. The A2 sight consists of two apertures; a large short-range aperture for use to 200 meters, and a small aperture for 300 to 800 meters. For targets 300 meters and beyond, the elevation adjustment wheel is used to match the target's distance. A large windage adjustment knob is present on the right-hand side of the sight. These sights are near ideal for target shooting, where the targets are known distance or there is ample time to determine the range, adjust the rights, dope the wind and dial windage, then make the shot. The adjustments are rarely used in combat and can present a liability due to ease of getting knocked off zero. I have heard reports of the elevation wheel bumping up one click under recoil and causing the point of impact to rise. On a fighting rifle, witness marks should be used to indicate correct zero position when using the A2 sight.