I really don't understand why 5.56 NATO ammo would be "unsafe" in a .223 chambered AR, either.
They both use the same barrel blanks and bolt.
The 5.56 NATO is small-base sized, so it's going to chamber loose in either one.
Other than the 5.56 only being available in FMJ, I don't see the problem. /ubbthreads/images/graemlins/confused1.gif
If you've got a bolt gun chambered in .223, all bets are off.
You guys are aware there are such things as "proof" rounds, correct? /ubbthreads/images/graemlins/crazy.gif
Quote:
Each weapon and component considered vulnerable to the effects of a rapid change in pressure, for example barrels, breech blocks and bolts, will be tested by firing one dry round at a corrected minimum of 25% over pressure and one oiled round at a corrected minimum of 25% over pressure. 25% over pressure means 25% in excess of the Service Pressure (Pmax). The Service Pressure is defined as the mean pressure generated by the Service Cartridge at a temperature of 21°C. Such a high pressure proof is conducted with both the weapon and ammunition conditioned to an ambient temperature of 21°C.
Each weapon will be individually tested, from an ammunition lot that produces a minimum corrected mean chamber pressure in accordance with the table below:[1]
Corrected Proof Pressure Requirement (Service Pressure (Pmax) + 25%)
5.56 mm (5.56x45mm NATO) Designed to chamber NATO ammunition Service Pressure Pmax (MPa / (psi) 430 / (62,366)
Proof Round Pressure Requirement (MPa / (psi) 537.5 / (77,958)
Pressure recorded in NATO design EPVAT Barrel with Kistler 6215 Transducer or by equipment to Commission Internationale Permanente pour l’épreuve des Armes á Feu Portatives (C.I.P.) requirements