I was out shooting my colt(series 80 govt) yesterday and it was running well untill about the fourth mag. My pistol went to slide lock on the second to last shot. The gun ejected the spent case and locked with a round still in the gun. This round didnt chamber and was sitting free in the gun. Most internals are up-grades and i am using wilson etms. the pistol ran great the rest of the day. Has this happened to anyone or does anybody know why this happened.
I would guess that either the top round in the magazine pushed up on the slide stop during the feed process or that your thumb/hand accidentally hit the slide stop during the recoil.
Had this same exact problem recently with a new Combat Elite (even after more than 500 rounds). Happened with several types of mags, but mostly with some McCormick eight round mags. Got several suggestions about the gun including trying a new slide stop or mags. Went with the advice of purchasing some Tripp research 7 round kits for my McCormick mags. While I was at it, I bought one of their 8 rounders too. With very little range time through the new set up it appears to have cured the problem. Will shoot more to confirm. Hope this helps.