instead, it uses 6061-T6 aluminium to form the upper and lower receivers. This rifle ships with an adaptor to mount AR-15 style stocks (and comes with a collapsible AR15 stock). As Length of pull (LOP) is long with many AR15 stocks, some users have retrofit Cz Vz58 folding stocks to these rifles. While this option works well, it requires the use of lower iron sights and optics. In 2019 Brownells, Inc. released BRN-180 complete upper assembly, a new take on the AR-180 design built around the AR-18 short-stroke piston system. The BRN-180 is designed to be fitted to mil-spec AR-15 lower receivers and unlike standard AR-15s the BRN-180 can be fired with the stock folded. The BRN-180 comes with an adjustable gas block and a free-floating modular handguard and is available in barrel lengths. Influence When the AR-18 was designed, a plethora of different methods of gas and recoil operation existed in self-loading intermediate caliber rifles. Since then, self-loading intermediate caliber rifles have converged toward three methods of gas operation. These are: AR-15 style direct Impingement, the AK-style long stroke gas piston and the short-stroke gas system found in the AR-18 rifle. While the AK and AR-15 are the first and second most produced intermediate caliber rifles of all time, the AR-18 gas system is the ancestor for the majority of short stroke gas systems found in selective fire military rifles. The AR-18 mechanism is the basis for many rifles in major military service. Rifles which use a copy or derivative of the AR-18 gas system include: German HK G36, HK416, FN F2000, FN-SCAR, Steyr AUG, CZ 805 BREN, Chinese QBZ-95, Daewoo K1, HOWA Type 89, SAR-88, T-91 and British SA80 family of weapon systems. In some cases, designs borrow more than just the AR-18's gas system. Successive rifle designs borrow other components such as the bolt carrier group or upper receiver. The HOWA Type 89 is an AR-18, modernized to fit the needs of the Japan Self-Defense Forces. The Singapore SAR-88 and Taiwanese T-91 utilize a complete AR-18 upper receiver. Early British SA80 prototypes featured ArmaLite produced AR-18 upper receivers mated to a prototype stamped metal bullpup lower receiver. The finalized SA80 weapon systems use the AR-18 gas system and bolt carrier group. The Remington Adaptive Combat Rifle derives its bolt carrier group from the AR-18. Users : Used by the Royal Malaysian Air Force. For trials : Tested