I try to be careful but one time I accidently found out that a 45 SIG will accept into the magazine, feed, chamber, and fire a 40 s&w round. The case swelled to 45 but apparantly didn't damage the gun (It was 2 years ago) So don't do what I did. It is easy to do when you are shooting both calibers at the same time. I won't do it again. I was lucky that time.
