AR-57

The AR-57 is an American rifle system built around the FN 5.7x28mm cartridge and fed from the standard magazines of the FN P90. It is sold either as an upper receiver that fits the lower receiver of an AR-15 or M16 rifle, or as a complete rifle supplied with two 50-round P90 magazines. The design was originally by Rhineland Arms and is produced by AR57 LLC. Unlike the standard AR-15 layout with its gas tube, it cycles by straight blowback. The magazines sit horizontally on top of the front handguard, and spent brass is ejected through the magazine well. A Picatinny rail carries scopes and other accessories. A fully automatic version exists and was marketed as a competitor to the P90 and other personal defense weapons, and suppressed versions are also available. Venezuelan soldiers who defected to Juan Guaido were photographed using an AR-57 during the 2019 crisis in Venezuela.