03-27-2014, 02:58 AM
.223 Remington is SAAMI MAP rated to 55,000psi, whereas 5.56 NATO is a 62,000psi cartridge and chamber. Two different animals from a pressure containment standpoint.
The original .222 Remington is rated to 50,000psi MAP, and that is what the AR15 was built around when it was just a prototype in Armalite's solicited development for the High Velocity Small Caliber Rifle contender for the Army.
The original .222 Remington is rated to 50,000psi MAP, and that is what the AR15 was built around when it was just a prototype in Armalite's solicited development for the High Velocity Small Caliber Rifle contender for the Army.