I'm going to have the slide on my 1991-A1 tightened to go with the new barrel installed. I was told that sometimes the stainless steel used in 1991s is so hard that it is almost brittle and can break. Is this true? Also, why is th frame squeezed for 20 seconds and then stress relieved(whatever that is) by rapping on the flat anvil part of the vise with a hammer? Any information anyone could give me would be much appreciated. The 1991 I'm building is for kicks, not self defense, but I would hate to have the slide ruined nontheless.