Since 1928, Prvi Partizan has been producing custom ammunition in Serbia for competition, indoor ranges and hunting. Full metal jacketbullets are non-expanding rounds that were designed for target shooting because of their good penetration ability. This ammunition is new product, non-corrosive, in boxer primed, reloadable brass cases.Please Note: While the 5.56x45mm NATO will fit in a .223 Remington chamber, the 5.56 is a military round that runs at higher pressures than its .223 counterpart and is not recommended to be fired in a .223 Remington chamber.Specifications: Caliber: 5.56x45mm NATO Bullet Weight: 55 Grains Bullet Style: M193 Full Metal Jacket Case Type: Brass Muzzle Velocity: 3248 fps Muzzle Energy: 1283 ft. lbs.