Federal Premium’s® .50-cal. 270-gr. Trophy Copper Muzzleloader Bullets with the exclusive B.O.R. Lock MZ™ System provide outstanding accuracy in a non-sabot design. They are easy to load, scrub fouling from the breech and ensure consistent bullet seating. The foundation is a polymer cup permanently attached to the bullet base. Force of ignition pushes the cup onto raised bands along the bullet shank, expanding its diameter which engages the rifling and seals the bore, optimizing velocity and accuracy. At the rear of the B.O.R. Lock MZ cup is a hard, fiber-reinforced polymer ring that scours fouling from the breech as the bullet is pushed into place. This decreases the need to clean between shots and makes it easy to seat the bullet at the same depth for every shot. With no bulky sabot, required loading force averages about half of most sabot bullets. This copper-alloy bullet features a polymer tip, with a deep, hollow cavity and skiving for consistent, devastating expansion. Per 15.