I have a Thompson Auto Ordinance 1911A1 that I bought at some time in the 90's. I've been off and on at shooting it and over time I've played around at improving it, trigger job molybdenum refinish, new grips, etc. It turned out to be a good shooter and its fun to shoot. The puzzler is....the pin that holds the mainspring housing in the frame breaks every couple of hundred rounds. Just snaps it two. I've replaced it several times and I now order the pins in 6 packs. I can't envision that it is under any stress other than the downward pressure from the mainspring. What snaps it??