Frontier Cartridge Lake City, 223 Rem, 55 Grain, Full Metal Jacket, 150 Round Box FR1015 Frontier(R) Cartridge features Hornady bullets and is available in 223 Rem, 5.56 NATO, 300 Blackout and 6.5 Grendel. Applications range from plinking, target shooting and hunting to law enforcement training and self-defense.