ArmaLite AR-10A4: The Ultimate 7.62mm CQB Carbine!
By Christopher R. Bartocci

Normally the terms CQB (Close Quarters Battle) Carbine and 7.62x51mm do not go together. It is just not practical to apply this full powered battle cartridge into a compact package. The greater range and penetration of the 7.62x51mm cartridge have proven themselves practical in both Iraq and Afghanistan. With combat operations in the desert, the opportunity for longer range shots beyond 400 meters presents themselves on a regular basis. There has been an unofficial need for a shorter, more compact 7.62x51mm rifle. Carbines chambered in the NATO cartridge have been attempted in the past by manufacturers such as Heckler & Koch, Springfield Armory, FN and others, but through all the attempts, you just can not tame the heavy recoil for CQB scenarios - until now.

With the sunset last year of the 1994 Assault Weapon Ban, Mark Westrom, president of ArmaLite, Inc., went to work to put his AR-10 series of rifles into the now legal pre-ban configuration. Prior to that, Knight's Armament put out limited numbers of their SR-25 in a carbine configuration but they were very pricey and hard to get hold of for civilian use. Westrom and ArmaLite, Inc. have produced more AR-10-type weapons than all the other manufacturers combined including ArmaLite Division of Fairchild Engine and Aircraft, Artillerie Inrichtingen and Knight's Armament. Westrom produces a better rifle designed to be in 7.62mm at a much lower cost and his new carbine is no exception.

The new AR-10A4 carbine takes the look and feel of the popular M4 carbine and puts it into the 7.62x51mm caliber cartridge. This enables one to switch from the 5.56x45mm to the 7.62x51mm with no additional training. The operator who is used to one will be right at home with the other. With the ban lifted, Westrom was free to put on the telescopic stock and flash suppressor.

The AR-10A4 sample sent for evaluation had a Mil-Std 1913 rail on top of the gas block. With the rifle came a new ArmaLite developed detachable folding front sight assembly that utilizes a square front sight post inside a protected ring and is adjustable for elevation. The rifle also came with an ArmaLite developed emergency back-up sight. The rear sight flips up but does not lock in place; it was designed for emergency use, and is intended to fold out of the way without damage if run into an object. The actual aperture is round and controlled by a dial on top of the sight allowing several different aperture sizes to be used. If one wanted to use the iron sights primarily, ArmaLite offers the detachable carrying handle and front sight similar to the sights of an M16A2. The upper receiver comes with two different handguard systems. One is the standard mid-length handguard which comes in both black and green. The other is a specially designed A.R.M.S., Inc. SIR system. The test sample provided was equipped with the SIR system.

The upper receiver utilizes the Swan developed Mil-Standard 1913 rail on a flat top upper receiver with an integral fired cartridge case deflector. All of Westrom's AR-10-series rifles omit the unnecessary forward assist assembly and all of the current production AR-10 rifles utilize the extended feed ramps on both the barrel extension and upper receiver as is found on the M4 carbine. This assists mainly with the use of thin jacketed match grade bullets so they do not get damaged during the feeding cycle.

The barrel is 16 inches with a 1 turn in 11.25-inch twist. The barrel is chrome lined in both the bore and chamber. The AR-10 carbines use a mid length gas tube that was developed by Mark Westrom. As with the 5.56mm counterparts, the short standard carbine gas tube sped up the operating cycle of the rifle possibly increasing the cyclic rate by more than 200 rounds per minute. This is much harder on the operating system causing failures to extract and eject, as well as reducing bolt life. By utilizing the mid length gas tube, the gas port location is increased from the standard carbine and placed approximately in-between the distance from the carbine gas port location and the location of the gas port on standard rifle. This lowers the cycle time; giving the fired cartridge case more time to contract (lower residual pressure) before being extracted. With the lower cycle rate, there is less punishment of the bolt. This is an improvement Westrom offers in both 5.56x45mm and 7.62x51mm calibers. The barrel also comes with a standard M16A2-style compensator with the solid bottom.

The lower receiver is the standard forged ArmaLite AR-10A4 lower receiver with the addition of a six-position telescopic butt stock featuring a receiver extension specially dimensioned to suit the AR-10. These stocks come in both black and green. Fixed stocks can be utilized on the ArmaLite carbine as well. One of the more recent changes Westrom has implemented is the standardization in trigger components between the AR-10 and his M15 5.56x45mm rifles. During the development phases, the AR-10-series rifles was built very much like the SR-25 so major components could be interchanged. One of these parts was the hammer. The hammer was much narrower in width and the slot in the bolt carrier would correspond, so the standard M16/AR-15/M15 hammer could not be used. Recently, ArmaLite has replaced the AR-10 hammers with standard dimension M16/AR-15/M15 hammers as well as modified the bolt carrier to accept the standard hammer. ArmaLite offers both a standard trigger as well as a 2-stage match grade trigger.

The bolt carrier group has changed little since the development of the new AR-10 family of rifles in 1993. The main change is the modification to allow the use of a standard size hammer. The extractor has been modified having a significantly stronger and more durable spring assembly. The carbine extractor utilizes two springs. One is nested in the middle of the other. On top of that is a rubber "O" ring that was developed by SOCOM for use with the M4 carbine to increases the extractor force. This combination along with the mid-length gas system makes an extremely reliable carbine.

The A.R.M.S., Inc. SIR System

The Selective Integrated Rail (SIR) system is the most significant advancement for this weapon system since the development of the M4 carbine. This is a rail system which offers some major advantages over conventional handguards. First, and most importantly, it allows the barrel to free-float. The SIR system attaches directly to the barrel nut and to the flat top upper receiver. Free-floating the barrel gives two main advantages: it increases accuracy by keeping accuracy-reducing contacts from altering the natural barrel vibrations and it increases the cooling capability of the rifle. This is particularly important in the fully-automatic M4 carbines. The cook-off and the heat threshold of the barrel are significantly increased. Due to the free floating any accessory may be hung on the handguard as well as a vertical pistol grip without putting pressure on the barrel. The bottom of the handguard may be removed for cleaning or for installing an M203 grenade launcher. The sleeve of the SIR System protects the rail on the upper receiver from the possibility of damage.

Shooting the AR-10A4

The sight chosen was the EOTech Holographic sight. This is a reflex sight with a red circle with a dot in the middle. The intensity of the reticle can be adjusted according to the external light conditions. The EOTech sight is one of the finest choices available for close shooting under stressful conditions. Due to the large screen of the sight both eyes can be left open allowing full peripheral vision to be used. This sight has achieved much well earned success for its tactical flexibility and quick target acquisition capabilities. Due to this being a holographic sight, it does not matter how you look through the window/screen, wherever the dot is the bullet will go. No matter if there is mud, dirt, snow or even if it is broken. If an area of the screen is still intact the holograph sight will be there.

More than 300 rounds were fired with no malfunctions with several different generations of magazines being used. The ammunition used was Lake City M80 Ball, PMC 180-grain JSP and some of my own reloads which utilized a 147-grain FMJ bullet. The carbine even handled the American Eagle .308 Win., which is often produced at a shorter overall length that is not well tolerated by AR's. The carbine functioned flawlessly with all it was fed. Recoil was noticeably more that the 5.56mm but not uncomfortable by any means. However, the carbine would benefit much more from a muzzle break than a flash suppressor.

A vertical pistol grip (A.R.M.S. #23 Quick Detach Throw Lever Pistol Grip) was added for CQB scenarios. The conditions were 15 to 25 yards on standard IPSC targets. Double taps were consistently kept within the A and B zones in the targets. It is believed the in-line design of the Stoner developed gas system/rifle gave a controllability edge over other rifles in the same caliber for this purpose. Any more than a double tap and the shots would get away. One can only imagine how this would be if the carbine was fully-automatic. This was quite good for the caliber and size of the rifle. Off the bench at 100 yards using Winchester Supreme 168-grain match ammunition, the carbine consistently achieved 1.5-inch groups.


Overall, the AR-10A4 carbine was very impressive. It has the quality and finish that ArmaLite is known for. The AR-10 rifles continue to be upgraded and improved by Westrom and ArmaLite. For one who is fond of the AR-15/M16/ M4 carbine weapon systems and is just not fond of the 5.56x45mm caliber, here is the answer to your problem. This is a reliable and compact 7.62x51mm caliber rifle that is reasonably priced and second to none. ArmaLite offers an AR-10A2 carbine as well which features fixed M16A2-style fully adjustable rear sight.

AR-10A4 Carbine

Caliber: .308 / 7.62mm
Upper receiver: Forged flat top
Trigger: Standard
Barrel: 16-inch chrome lined
Rifling twist: 1:11.25 inches
Front sight base: Gas block
Muzzle device: Flash suppressor
Overall length: 37.1 inches
Weight: 9 pounds
Accuracy: 1.5-2 MOA at 100 yards


ArmaLite, Incorporated
P.O. Box 299
Geneseo, IL. 61254
(309) 944-6949

A.R.M.S., Inc.
Atlantic Research and Marketing Systems, Inc.
230 West Center Street
West Bridgewater, MA 02379
(508) 584-7816

EOTech, Inc.
Electro-Optics Technologies
3600 Green Court, Suite 400
Ann Arbor, MI 48105-1570
(734) 741-8868

This article first appeared in Small Arms Review V10N5 (February 2007)
and was posted online on December 14, 2012


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