As its Type 821 submachine gun was based on the famous Israeli UZI 9mm, SOCIMI (Societa Costruzioni Industriali Milano) of Italy attempted to sell another automatic weapon based on a popular, existing design - the AR-831 born of the AR-15/M16. Design work began in 1985 and the weapon retained certain qualities consistent with the original product - namely its 5.56x45mm NATO chambering, STANAG magazine feeding, over-receiver integral carrying handle, and fixed stock to name a few. It differed in its operation via a gas system as opposed to the direct impingement piston system of the AR-15/M16 family. In essence, the AR-731 was anM16 with a Soviet Kalashnikov AK-47-style system of operation.
As SOCIMI lacked industry know-how to produce such a rifle from scratch, it enlisted the help of Italian firearms maker Luigi Franchi of Brescia to develop its AR-831, the Type 821 SMG, and the AR-832 Battle Rifle that followed. SOCIMI was one of many other new concerns appearing during the height of the Cold War attempting to cash in on the popularity of NATO-standard firearms.
The AR-831 was developed with the intent on improving the reliability of the AR-15/M16 action and thusly a gas-operated system was selected which mimicked that of the AK-47. The AR-831 lacked the forward bolt-assist of the AR-15/M16 and utilized a three-position M16-style fire selector. A fixed stock and folding stock (Para model) version were eventually developed from the base AR-831 design to which the folding stock variant relocated its recoil spring from the stock area to the gas cylinder (as in the AK-47). Iron sights were standard on both and charging of the weapon was through an M16-style pull system found at the rear of the upper receiver. The rifle was also inherently capable of firing rifle grenades and featured a tool-less field stripping design. It fed from 20- or 30-round STANAG magazines.
The AR-871 of 1987 became an improved form of the original AR-831 and added a gas-operated rotating bolt internal action that locked into the barrel extension while introducing a more conventional, left-handed charging handle along the side of the receiver. All other functions remained faithful to the original product though streamlining was readily apparent with the newer model.
The AR-831 did not find many takers on the open market.