NO! It was out of proof when it would accept the next larger gage than stamped on its bbl. That's why the system was eventually changed, as unless the actual bore dia was marked there was no real way of knowing if a bbl marked 13/1 was proofed at .720" or 728". Thus when it accepted that 12 gage (.729") it was out of proof.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra