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Join Date: Jun 2009
Location: Northern Berks County, PA
What you have to understand/recognize is that there is no heavenly divined max charge for a given powder/projectile/cartridge.
In fact, the max for a given projectile could even vary a smidge from chamber to chamber and even from brand of brass to another brand of brass.
Then there is the pressure max that each manual's creators decided was their "red line". It may or may not be the same for each manual.
Bottom line is that the maxes you see are a product of how each manual's technical content folks decided to specify just what constitutes a max charge.
Put it in a hunting analogy--
Let's say there was a law that an antlered deer for tagging purposes is one that has antlers. No further guidance is given. Just that it's a hard/fast rule that a deer possessing antlers is considered antlered.
One person says, "an antler is anything with three branched points."
Another says, "Anything that is bone above the hair."
A third says, "A spike at least 3" long."
The "rule" was it has to have antlers. Each person interpreted the rule in a way that complies with the rule, but varies from the interpretation of the others.
The "deer has to have antlers" is SAAMI's max pressure for the round. I can't possibly imagine any manual in existence will post data that is at all capable of coming near that threshold.
BUT.... how close to it do they go? Ah, there's the question. Your 308 data may be capped at 50,000psi. Maybe 55,000. Maybe 48,000. That'll cause a lot of variation in what the published charges look like.