Masterpiece Arms SR556 (MPAR 556)

This rifle is a MasterPiece Arms MPAR 556 Sporting Rifle. The MPAR Sports a heavy stamped-steel receiver, 16-inch barrel with a 1:9 twist. The MPAR 556 employs a short-stroke piston action enclosed by a lightweight, free-floating, two-piece, hard-anodized aluminum handguard. The Gas Piston system delivers the ultimate in reliability over the AR15 Gas Impingement system.

Furthermore, this rifle keeps on jamming.