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Old March 9, 2013, 10:05 AM   #6
Bart B.
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Join Date: February 15, 2009
Posts: 4,830
Rainbow Demon, you are so right about some long range loads being a bit much for some rifles. In the USA arsenals specs, average peak pressure for the 7.62 NATO's 50,000 CUP. But the military teams oft times went beyond that.

That articles reference to replacing M80 ammo's 147-gr. ball bullet with a Sierra 168 ended up with a round with almost MIL SPEC proof load pressures. The proof load was a 172-gr. match bullet atop 41 grains of IMR4475 stick powder; the powder used in M80 ammo that was the favorite for swapping bullets on. It produced 65,000 CUP and with the 168, about the same. But the M14's and M1's shooting it had no problems as their receivers are robust enough to easily handle it. And with well fit operating rods, they stayed straight. I've shot that "proof" load in matches pulling bullets from those M80 lots and replacing them with 172's pulled to make the load shown below.

That US Air Force load with 44 grains of IMR4320 under a Sierra 190 in a new primed M118 match ammo case was the most accurate load for long range ever used in M1 Garands rebarreled to 7 .62 NATO. I've known its US Air Force Rifle Team developer since 1965 and he shared it with the USN Rifle Team. In a conversation about that load with a ballistics engineer at Lake City Army Ammo Plant back in the '70's, he said that load was no doubt over 60,000 CUP.
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