Paul, yes the thread drifted. And yes, crimp depth does affect pressure. However, when we are discussing Parkers, chamber pressure, in my opinion, should play little part unless a person is seeking to load up to maximum service pressure. We know what or about what those are for each gauge, but most of us, myself included, seldom shoot max pressure shells. The Parker max service load is more than we want or generally need to shoot, but its there if we need it unless the gun in question is loose, bored out, bad stock or otherwise in poor condition. I don't have guns like that but I know some do.
We have posters who somehow seize upon 5000psi as a magic number for 12ga chamber pressure. I don't know where that comes from, maybe light 2 " British guns, but not Parkers and its not a Parker number at all. Parker told us what to shoot with a range of acceptable loads which are still available today. For me, that's what I follow.
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