|Place of origin||Italy|
|Manufacturer||Societa Costruzioni Industriali Milano, Luigi Franchi S.p.A.|
|Feed system||30-round detachable STANAG magazine|
The AR-831 is the second weapon developed and produced by SOCIMI, chambered for the 5.56×45mm NATO round. Once again in designing the AR-831 assault rifle, SOCIMI chose to improve upon an existing popular design, the M16 assault rifle. Although similar externally, there were some mechanical improvements incorporated in the AR-831 to make the weapon more reliable when exposed to extreme climatic conditions such as mud, snow, sand and dust. Arguably, the weakness of the US combat rifle is its direct gas impingement, which is easily affected by entry of foreign matter.
The Italian engineers at SOCIMI realized the shortcomings of the US rifle and came out with an improved M16-type rifle in the form of the AR-831. The new rifle, which they developed in 1985, used an AK-47-type gas piston, which is directly mounted at the top of the bolt carrier, but with the bolt and bolt carrier identical to that of the M16, as well as the recoil spring, recoil spring guide, magazine catch and hold-open device. The cocking handle and trigger section are slightly different in format but function and connect in the same manner. The standard 20- and 30-round STANAG magazines are used. There is a slight variation in plastic furniture design, as well as the angle of the pistol grip that is of finger groove pattern. The 3-position fire selector is derived from the original M16 and can only be operated by right-handed shooters. Unlike the M16, there is no forward bolt assist on the AR-831 as it is not needed due to its superior AK-47 gas piston operation. Additionally, the weapon comes with a gas regulator, which also controls the rate of fire, and also allows the use of rifle grenades. A folding stock variant of the AR-831 is also offered patterned after the Belgian FN FAL Para carbine. In the fixed stock version, the recoil spring is housed inside a large tube that also doubles as a connecting base for the plastic buttstock. In the Para variant, the recoil spring is assembled inside the gas piston like on the AK-47 design.
In 1987, an improved version of the SOCIMI AR-831 assault rifle was introduced as the model AR-871. The refined version is a selective-fire weapon using a gas-operated rotating bolt that locks directly into the barrel extension. The rifle is produced in various formats with a variety of fire selection systems, allowing semi or full-automatic fire, semiautomatic or three-shot burst or semiautomatic-only. The weapon retained the original straight stock configuration along with a long stroke bolt cycle that provided mild recoil. The rifle is light and rugged with majority of the components being made of light alloy forgings, hi-impact resistant polymer and high tensile steel. The cocking handle is on the left side of the receiver. The original design had the cocking handle on the top rear of the receiver A la M16. The magazine release is ambidextrous on the AR-871. The barrel is chrome lined and the muzzle is capable of launching rifle grenades. Both the original AR-831 and the AR-871 assault rifles can be field stripped quickly and easily without the need of tools starting with the removal of the rear connecting pin (like the M16) and hinge open the action to pull out the bolt and carrier assembly. However, it can be easily stripped in minutes (except trigger group) of its sub-components (buttstock, handguard, gas piston and flash hider groups) using only the rim and point of a cartridge as a tool if a more detailed cleaning is required.