Black Hills produces factory new ammunition equal to some of the best handloads and is quickly becoming one of most popular manufacturers of ammunition. Used primarily by all branches of the United State military, this ammunition is also used by competitive shooters and hunters. MatchKing bullets have very thin jackets and are held to exacting tolerances in diameter and weight. Their accuracy has been acclaimed worldwide and they have been used to win more target competitions than all target bullets from other manufacturers combined. This ammunition is new production, in non-corrosive, in boxer-primed, reloadable brass cases. Please Note: While the 5.56x45mm 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.