Thanks all for the comments and past experiences - that's why I asked the question, as I knew someone that was smarter than me could explain the do's and don'ts.
With that said, I'm not really trying to hot rod the 7.62x39, just trying to determine if its safe to increase pressure a bit based on firearm strength vs brass strength. As reloading loonys, we all like to tinker with things - that's why we reload :-). I have plenty of other guns in more powerful chamberings, so I completely understand if I really want more power, get a bigger stick!
In the end, think of the example I mentioned before - the classic 45/70. If someone didn't "go off script", we wouldn't have 3 different load levels for it, we would be stuck with the Trapdoor loads (not that there's anything wrong with those!) I could have used any cartridge that was deliberately loaded to lower pressures due to the firearm it was designed for....say the 280 Rem, 7x57, etc.
Thanks again for all the comments and information - that's why I'm here - to learn for those who have "been there, done that" :-)
Merry Christmas and Happy New Year to all!
