AR57 LLC

AR57 LLC manufactures the AR-57, a 5.7×28mm upper receiver and complete carbine system built to mount on a standard AR-15/M16 lower. The design originated with Rhineland Arms, a small US shop that built and refined the first prototypes; AR57 LLC took over production and continues to sell the system as both a drop-in upper and a complete rifle through its own online storefront. No free source publishes a founding year for either company, so none is recorded here.