ArmaLite AR-16

After the relative success of the 7.62x51mm AR-10 and the subsequent 5.56x45mm AR-15′s sale to Colt, Eugene Stoner began work on another weapon, the AR-12.

The AR-12, chambered in 7.62x51mm, was merely a previously unused concept until 1959-60 and after a short development was subsequently abandoned before the prototype was finished. ArmaLite had intended the AR-12 to be simpler and cheaper to manufacture, than the more expensive AR-10, so it could be marketed to poorer nations. However, with the licensing of the gas impingement system (US #2,951,424) and the AR-10 and AR-15 designs to Colt in February 1959, Stoner was forced to begin work on an alternative action, a short-stroke gas piston system, to avoid infringing the licensed patent.

In the subsequent AR-16, Stoner used a short-stroke gas piston with a captive dual recoil spring assembly. Retaining the AR-12′s 7.62x51mm chambering, prototypes of the new rifle were made with both rifle and carbine (16.1 inch) length barrels. It fed from a 20-round steel box magazine rather than the AR-10′s aluminium ‘waffle magazines’. Rather than have an extended magazine housing the AR-16′s magazine’s rocked and locked in. The rotating, cammed, multi-lug bolt developed with Melvin Johnson’s assistance was retained but mounted on a, cheaper to machine, square bolt carrier. The basic design is covered in the first page of Stoner’s later Stoner 63 patent (US #3,198,076).

As in his earlier work Stoner continued to work on the concept of modularity with an earlier technical drawing showing how with the AR-16′s hinged upper removed the lower might be paired with a 7.62x39mm or 9x19mm submachine gun upper. 

The AR-16 with its folding stock folded (source)

The AR-16′s receiver was made from stamped sheet metal and was welded and riveted together. Unlike the AR-10 and early AR-15′s the cocking handle was moved from the top of the receiver to the side to simplify manufacture. While the AR-16′s design was promising the increasing interest in lighter rifles chambered in 5.56x45mm led to its abandonment until Stoner left the company in 1961.   

After Stoner departed ArmaLite, to work on what would become the Stoner 63 at Cadillac Gage, Arthur Miller took over as ArmaLite’s lead designer. Miller took Stoner’s 7.62x51mm AR-16 and redesigned it to chamber the smaller 5.56x45mm round to create the AR-18 (US #3,246,567). 

ArmaLite promotional photograph showing a fixed stock, longer barrelled AR-16 (source)

The similarities and shared lineage with the later Stoner 63 and AR-18 is clear to see in not just the stamped receiver’s shape but also in the folding stock mechanism, rear sight and gas block. Unlike the AR-10 and late AR-18, the AR-16 prototypes had wooden rather than fibreglass or plastic furniture.

ArmaLite, Howa and Sterling all went on to produce the AR-18 and the semi-automatic AR-180 in moderate numbers. Only four of the original AR-16 prototypes were made, of these two are currently held by the Reed Knight Institute of Military Technology (see image #4). 

Sources:

Images: 1-3 4

The Armalite AR-10: World’s Finest Battle Rifle, J. Putnam Evans (2016)

Various Posts on AR-16,Gunlab.net, (source) - My Thanks to Chuck for the use of some of his photos

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