I have my G3 Glock 20 SF slam shut after the last round is fired sometimes. The first time it happened was after firing some semi hot 200 gr loads with the standard spring. I thought I needed a stronger spring. So I got a 20 lbs. But it kept slamming shut. The slide stop was also scuffed on the top. I got a new slide stop and the problem went away for a while. But it re-appeared. This time without me firing overly hot loads. Has anyone else experienced this, have any thoughts what might cause it... Did I damage my gun permanently with the 200 gr hot loads that 1st time.