I just don't know what was official from all the different numbers. My assumption was the CIP borrowed the military specs (why make up a different spec) as they do with their drawings of the NATO rounds. But it's really the existence of those slugged .305's that made me think the guy who said the groove diameter was .3047" might be right or might have been right about one point in its history. They only made about half a million, I think, but I don't know if the design changed at any during production. At any rate, it seems like stopping a .308 on the freebore is quite possible if you have the narrow bore, assuming the chamber reamers were made to match. I just need a chamber cast or slug to be sure.
Every once in awhile you hear of someone successfully shooting a .308 bullet through a 7 mm rifle without permanent damage. Not something you can count on getting away with, but the smaller difference in the 7.5, however real it is, doesn't matter much by comparison. I wouldn't expect it to be a problem up to 0.005" difference or so.
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