Hello, I'm working on a buddy's Mossberg 500 AT Pump 12ga., 30+ years old. He claims that once a round is loaded in the chamber with the bolt closed, that as soon as he flips the safety off, the gun will fire immediately without a trigger pull. Very strange, i did a few dry runs of priming the firing pin and flipping the safety on and off, but never heard the firing pin actually go off. It will dry fire normally with a trigger pull, but I was wondering if this is even possible with older Mossberg 500 models? I took everything apart and it all looks good to my knowledge. Going to take it out to shoot and see if i can replicate the problem, but I cant see how the safety switch could possibly activate the firing pin and make a round go off. Anybody ever heard of this problem with 500s? Any info on the gun would be appreciated! Thanks!