here is my question... does anybody have any idea what the test pressures were when these guns were originally manufactured.
Typically proofing a gun they use much hotter loads to make sure it's going to be safe.
I'm trying to determine if it would be safe to use
+ P or +P+ ammunition if I can find it on the market
I have no first hand knowledge proofing, test pressures or reloading for that matter.
Logic would certainly discourage me from attempting heavier loads in a small automatic pistol for safety reasons as you mention.
I suspect the later Model 1917's are more robust than the earlier 1907's, but, ...
Perhaps someone with some first hand knowledge will chime in with some input, but until then you are on your own.
I know a guy who carries a Ruger LCP 380. Portable and decent power.