Yes, the gun wasn't made to handle high pressure 2 3/4" American loads such as Remington or even worse, Reminton Express plus gobs of other American and Continental shells. Proof is a whole other subject, but if it was a gun that had undergone proof, it would no longer be in proof. It might be even dangerous to lengthen chambers if wall thickness there isn't adequate. Just don't do it and shoot the RST's like you talked about in your other thread.

Socialism is almost the worst.