The ArmaLite AR-10 marked the genesis of a new age of assault rifle – one that would eventually fill the need of replacing the outdated M1-Garand while offering up a lightweight alternative with magazine-fed firepower. While the original intent failed to deliver, the design was significant enough to spawn a field of similar rifles suitable for full-scale combat.
The AR-10 was a prototype introduced in 1955 by Eugene Stoner, a rifle design engineer who worked at ArmaLite, a small manufacturer with a machine shop in California. Initial testing proved to be a detriment to the success of the rifle, as it was structurally unsound to withstand the rigorous testing methods employed by the US Army. One of the standard tests ruptured the barrel as a result of heat that warped the gas tube. The barrel burst in the middle of the hand guard, and, even though the operator wasn’t injured, the potential for injury or catastrophic failure was clear at that stage of development.
While the overall success of the original ArmaLite AR-10 was peppered with failures and flaws, it did introduce several mechanical advantages and design elements that several modern firearms have adopted and perfected over time. Intended as a survival rifle for downed airmen, the AR-10 had lightweight receiver and barrel components intermingled with fiberglass-reinforced plastic. It adopted and modified the gas charging system of the M1 Garand with a few key differences and improvements.
The AR-10 platform introduced a gas impingement system, where propellant gas is channeled from a small hole in the barrel to the bolt carrier. The carrier then extracts the spent case and reloads the next round using spring tension. Gas impingement eliminated the need for piston-operated gas systems and all the associated parts. This system has proven itself over time, having been reintroduced into variations of the AR-10.
A signature design element of the AR-10 is the hinged takedown pivot point that separates the upper receiver from the lower receiver. It operates similar to a break-action shotgun, allowing easier access for cleaning and disassembly. This characteristic, along the straight-barrel configuration are the most obvious visual difference that sets the AR-10 family apart.
The lightweight platform and a solid majority of design elements were adopted into the AR-15 and M-16 used heavily by US forces during the Vietnam War. Production of the AR-10 was meek in comparison to its rifle variants because of early prototype failures during stringent stress tests. Where production of the M-16 reached 8 million units, only 9,900 original AR-10 rifles were produced. These rifles were mainly deployed by troops in Sudan and Portugal, seeing limited use during various civil wars and small-scale conflicts in the early 1960s and 1970s. The rifle was a mainstay for Sudanese forces for 27 years until 1985, though it is still in production today under different manufacturers, and geared toward civilian use.
Accuracy and efficiency were additional improvements over WWII-era rifles. High-velocity rounds could be cycled through at 700 rounds per minute with greater accuracy because of the straight-line stock design, which limited muzzle climb during rapid fire engagement. The rifle came fitted with adjustable rear sights and a fixed-post front sight. Final production rifles were chambered in 7.62X51 NATO rounds, or .308 Winchester, which were fed through detachable 20-round magazines. This doubled the capacity and the magazine feed eliminated the need for clip-style reloading.
Overall weight was another significant improvement. The production AR-10 weighed 7.25 lbs. which was 24 percent lighter than its predecessor. This allowed troops to maneuver longer distances with less fatigue. The key factors in the weight improvements were due to changes in the stock from wood to fiberglass-reinforced plastic, and in the receiver. The original prototype was made of a forged aluminum receiver machined to specification, and it had a 20.8” aluminum-steel composite barrel. Overall length was 41.3 inches and it weighed 6.85 lbs.
Early improvements included a reconfigured charging handle, improved barrel construction, and a better rotating bolt locking design. While these improvements helped to make the AR-10 function better over time, the botched testing early on prevented mass production and use by world powers over proven counterparts.
As a military option, the AR-10 never recovered from original testing failures in the United States despite the advantages offered through a lightweight system. However, modern enthusiasts have since jumped on the patent freedoms by running with the advantages of a lightweight rifle and chambering it with more sustainable rounds and materials that aren’t as self-destructive to the weapon.
Some variations of the AR platform have proven very successful in military service. Rifles like the Colt AR-15, the HK416, the M4, SIG 516, Ruger SR-556, and numerous other AR-style rifles all share characteristic design elements introduced by the AR-10. Modern AR-10 rifles produced by manufacturers including ArmaLite have since incorporated engineering improvements and patented components aimed at fixing the previous failures and building on the inherent strengths.
Improvements to the platform in the open market pushed the AR-10 beyond its own variation, the lighter, shorter, AR-15. The AR-15 boasts an impressive 60 rounds a minute with velocity of 3,150 feet per second in semi-auto mode, compared to 40 for the AR-10 at 2,690 feet per second. But where hunting is concerned, the AR-10 has a greater advantage with an effective range of 600 yards with open sights and 1,000 yards with a scope. The AR-15 is slightly less with an effective range of 525 yards and 800 yards, respectfully. Commercial pricing varies by brand and style, but the AR-10 is generally more expensive than the AR-15.
Modern AR-10s are similar in design, weight, and the better parts of performance. Civilian rifles have adopted tactical improvements, such as picatinny rails, barrel improvements, safety improvements, adjustable stocks, oversized barrels, shortened barrels, optics, and multiple calibers. The custom configuration aspects and ability to add modular accessories created a space for the AR-10 in the modern sport rifle for hunting and appearance while holding a place for tactical use by law enforcement. Gunsmiths and manufacturers both have embraced the platform as an opportunity to customize a sound design and re-brand the rifle to meet the market.