As American as 45Auto .223Rem (5.56x45) has been the standard round of the US military for over 55 years. - Developed for the original AR-15 .223 Remington has become one of the most popular sporting rounds with shooters and hunters in the United States. - This lightweight high-velocity round lends itself to being chambered with various styles of rifles from bolt action to semi-auto and belt-fed. - FMJ 55 Grain - Ballistic Coefficient (G1): 225 - Muzzle Velocity V0 ft/sec: 3261 - Muzzle Energy E0 J ft/lb: 1299 - Max Powder Pressure Bar (lb/inch2): 58015 - Cartridge Max Length: 2.26 inches - Cartridge Average Weight: 164 grains - Rounds per Box: 20 - Rounds per Case: 500