Frontier Cartridge Frontier, 6.5 Grendel, 123 Grain, Full Metal Jacket, 20 Round Box FR700 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.