Among many AR aficionados, it is believed that piston-driven rifles are a distinct improvement of direct-gas-impingement rifles like the ArmaLite-designed AR-15/M16. They like to quote many early Vietnam War-era marines who sniffed “Why would anyone want a rifle that bleeps where it feeds?” Those guys had a point at the time. The AR-15 (M16) was designed with ammo loaded with stick powders, but when the ammo contracts were awarded the GI ammo was loaded with ball powders which were much dirtier in terms of residue than the powders used in the development of the rifle. Consequently, the M16 had a well-deserved early reputation for jamming.
Former Marine and former Army Ordnance technician Eugene Stoner is considered the father of the AR-15 (M16), and he quickly realized the shortcomings of the gas-impingement system. Stoner’s final rifle design for ArmaLite, the 7.62-cal. AR-16 rifle combined his notions for improvement of the design utilizing David “Carbine” Williams’ short-stroke, gas-piston in a better caliber. The AR-16 was an effort to supply the U.S. military with a battle rifle less expensive to produce than the Garand or M14 rifles. However, soon after the adoption of the M14 rifle, Stoner left ArmaLite.
Another team of engineers headed by Arthur Miller began adapting the short-stroke piston design into a rifle of 5.56 NATO caliber in 1963. ArmaLite had sold the original AR-15 manufacturing license to Colt and wanted to get the production of U.S. military rifles into its house. Miller received U.S. Patent 3,246,567 on June 15, 1964, for what would become known as the AR-18 rifle. Five years later, a semi-automatic version—the AR-180—debuted for the U.S. civilian market.
The AR-18/180 was the latest iteration of the then-new method of rifle construction featuring stamped and welded steel fabrication. It is. for all intents and purposes. a scaled-down version of the 7.62 NATO-caliber ArmaLite AR-16. As mentioned, the AR-18/180 utilizes a short-stroke piston to facilitate operation. The rifle retains the familiar rotating bolt of the AR-15/M16, mounted in a carrier, but the carrier rides on a pair of guide rods. Instead of a buffer-spring unit contained in the buttstock as the AR-15/M16 has, the AR-18/180 utilizes a pair of action springs on the guide rods. You could say that the AR-18/180 is the more-or-less budget version of an AR-15/M16, which still used expensive forgings in its critical operation components. The AR-18/180 replaced most of these with stamped steel and welded components. Even the internal hammer is a stamping. The use of these stamped components required an increase in the tolerances, that some say leads to a slight increase in reliability in dirty environments, though this notion is by no means proven. A sliding, spring-loaded dust cover, also a stamping, offered some protection of the receiver from debris while the rifle was being transported.
AR-18 with stock folded. Image courtesy of IMFDB.
Other differences from the AR-15/M16 were an operation handle attached to the bolt carrier that traveled with the carrier during operation. The stock and fore-end of the AR-18/180 is somewhat lighter than the AR-15/M16, and the buttstock is hinged at the rear of the receiver assembly in an effort to ease portability in confined spaces. While this appeared to be a handy feature, in practice it proved to be a weak point in terms of stock stability as it relates to accurate fire. Barrel length on the AR-18/180 is 18" rather than 20", making the rifle slightly shorter, and thus a bit handier, than the AR-15/M16. The twist rate remained at 1 in 12" because the standard 55-gr. bullet was the only one considered for this rifle.
Magazines in the AR-18/180 have a different cutout and latching mechanism that prevents the use of AR-15/M16 magazines. The AR-15 magazines can be converted to function in the AR-18/180, but this is an additional expense and hassle that contributed to the ultimate failure of the AR-18/180 in the marketplace.
AR-18 with scope. Image courtesy of IMFDB.
The carrying handle atop the AR-15/M16 was jettisoned on the AR-18/180 since it found little use in the field and complicated the sight adjustment and trajectory computations. An iron sight similar to the one on the AR-15 was mounted directly at the rear of the receiver. A dovetail spot-welded to the receiver in front of the rear sight provided a way to mount a scope in ArmaLite proprietary rings, a concept way ahead of its time in 1964. ArmaLite marketed a 2.75x 20 mm telescopic sight with a quick-detachable, see-through mount that attached to the dovetail. Few of these, however, were sold.
Between the production contracts and politics, the M16 had an enormous and unreachable head start over the AR-18. Testing and evaluation trials at the Aberdeen Proving Ground in 1964 yielded some spotty results. Variations in accuracy and reliability with different lots of ammunition were the chief complaint. Those test results specified several changes and revisions needed to be made to improve reliability and safety. Further tests by the British Ministry of Defence in March 1966 found the AR-18 lacking in reliability in mud and sand environments. ArmaLite made many of the changes demanded by those review boards, but the appeal of a 5.56 NATO rifle seemed to have been sated for a time.
The SAR-87 was an advanced AR-18 derivative that was under development by Sterling Armaments of Dagenham. Image courtesy of IMFDB.
ArmaLite was an offshoot of the Fairchild Engine and Airplane Corporation, and its headquarters was in Hollywood, Calif., from 1954 through 1987. Another plant was opened in Costa Mesa, Calif., to produce the AR-18, but that facility was not sufficient for large production. Just 1,171 AR-18s and 4,018 AR-180s were made in Costa Mesa between 1969 and 1972. A production contract with Nederlandsche Wapen-en Munitiefabriek of Den Bosch, the Netherlands, was made, but few if any rifles resulted. ArmaLite was forced to contract the building of the AR-18 and the AR-180 to Howa in Japan, producing 3,927 AR-180s from 1970 through 1974, and later Sterling Armaments of Dagenham, Essex, in Britain, made 12,362 AR-180s between 1979 and 1985. Total production was just 21,478 AR-180s between 1969 and 1985.
Consequently, ArmaLite turned to the civilian market and focused its production of AR-180 rifles. A handful of AR-18s made their way into some law enforcement armories, as well as some third-world armies and security forces.
AR-180B. Image courtesy of IMFDB.
ArmaLite brand was purchased in 1996 by Eagle Arms, which changed its name to ArmaLite. In 2001 this “new” ArmaLite debuted an AR-180B, featuring a molded polymer lower receiver instead of the stamped-steel original. This lower receiver was combined with the buttstock, which was fixed on the AR-180B, replacing the side-folding stock on the original. The AR-180B adopted the AR-15 trigger group, along with the rear sight assembly. The dog-leg cocking handle of the original AR-18/180 was replaced with a straight one, and the sliding dust cover was deleted. This new hybrid, if you will, also utilized the AR-15 magazine release, allowing it to use standard AR-15 magazines. However, despite the changes—some of which were actual improvements—sales of the AR-180B floundered, and the rifle was discontinued in 2007.
In some ways, the AR-18/180 was ahead of its time. Clearly, the short-stroke piston and the ability to use optical sights on a rifle constructed from steel stampings and welded parts allowed for more reliability, better field accuracy and a lower cost of production. While its timing may have been unfortunate, given the issues of the world at that time, the fact that the AR-18/180 lacks the sleek lines of the AR-15 and the perception that welded steel stampings were not supposed to be on a rifle made for a real uphill battle for acceptance.
All that said, the AR-180 isn’t dead. There is a small, but dedicated, cult market for the rifle. It appears to be fueled by the lack of availability—relatively few were made, and it no longer is being produced. On the used market, an AR-180 will fetch between $900 and $2,500, depending on condition, rarity of variation—there aren’t too many of any consequence—and local market demand. It remains an interesting rabbit trail of modern rifle design and development that any student of firearms will want to pursue.