If you are going to put a double in to a vise, then it must a poor quality one. If it was made by a reputable maker, then after disassembly, checking the locking mechanism to the barrels and replacing any broken parts, I would gather some chamber and barrel dimensions and make a call. Last, use the correct shell length and appropiate charge. Whether you subscribe to Sherman Bells' school of thought or not, you should read "Find Out for Myself - Part XXII" Spring 2007. Although, shaving the barrel to around a couple of thousandths and using proof loads is a little much in my opinion. But obstructions are generally the culprit.
Kind Regards,
Raimey
rse
