Pro2a Tactical offers a unique line of 450 Bushmaster AR-15 NR Side Charging Upper Assemblies. The 450 Bushmaster is a hard hitting, straight walled cartridge, designed to be used in standard M16s and AR-15s. It is perfect for medium to large game and offers great penetration and stopping power at close distances. Pro2a Tactical 450 Bushmaster NRSC Uppers are carefully assembled by experienced armorers using the highest quality components and backed by our limited lifetime warranty.