The AR57, also known as the AR Five Seven, is available as either an upper receiver for the AR15/M16 rifle or a complete rifle, firing 57×28mm rounds from standard FN P90 magazines It was designed by AR57 LLC was produced by AR57 of Kent, Washington, USA The company is Description This is a FIVESEVEN 57x28 DEDICATED AR RIFLE chambered in the nasty little 57 caliber It uses a FnH magazine, which can be had in 10, 30, and 50 ROUNDS!!!AR15 MK57 BANSHEE 100 UPPER RECEIVER 57X28MM CMMG (In Stock) $000 50 (1) AR308 A3 STRIPPED UPPER RECEIVER LUTHAR LLC (In Stock) $ 00 AR308 UPPER RECEIVER 17 DESIGN AND MANUFACTURING (In Stock) $ 10 (1) AR15/M16 ASSEMBLED UPPER RECEIVER AERO PRECISION (In Stock) $9349 $ 47 (19) AR15/M16 STRIPPED UPPER Fn Ps90 5 7x28mm Bullpup Rifle Palmetto State Armory Ar 57 rifle price