I think there is a horsefly in the yogurt on your explanation as well, Jim. If one has a short chamber gun, and uses 2 3/4" ammunition, only to discover the cases ripped off down to the contact length at the cones, velocity will not automatically increase-but, recoil will. I suspect pressure would, also, but, I can't prove it.
A friend owns a French Charlin that rips the cases down to a bit below 2 1/2", sometimes even with European spec 65mm ammunition. To say the gun is unpleasant to shoot is an understatement.
Best
Ted
Your statement doesn't prove anything, either. There would obviously be SOME increase in pressure and likely some increase in velocity(if it's ripping the cases off). You don't say what length your imaginary chambers are but if your example even exists, they would probably have to be 2", in order to "rip off the 2-3/4" shell "down to the contact length at the cones". Ripping off part of a case that extends past the cone, into the bore is believable, not barely into the cone. Of course, you don't say what the chamber length of your friend's Charlin is, and more importantly, how much it weighs. I'll bet it is a very light gun. Ask him to lengthen the chambers and report back if the "unpleasant shooting" becomes pleasant. Maybe he's putting the shells too far into the chambers, resulting in the Gough Thomas recoil syndrome.
Best to you, as well
