I just picked up a gen 4 glock 20 the other day and after cleaning and lubing it took it to the range. I started out with light loads (180g American eagle and sellier & bellot) for about 100 rounds before going to some hotter stuff (sig 180g, grizzly 180g, and buffalo bore 180JHP and 220g hard cast. I cleaned it before going to the hotter rounds.
So the malfunction I'm seeing is about every 15 to 30 rounds after firing, the case is left half way inside the chamber, with the slide resting behind the next round in the mag which won't feed because of the previous case is still halfway in the chamber. This seemed to happen much more often with the grizzly, sig, and buffalo bore rounds.
Twice I also had the slide start to feed the next round and instead of pushing from the back of the case, it hit the middle of the case which shoved the nose of the bullet into the top of the chamber and jammed the gun.
I took video and saw no evidence of limp wristing but I'm not sure where to start. My thought is with the hotter loads the barrel is unlocking early and the case is still tight in the chamber causing the extractor to come off the rim of the case? Maybe I need a heavier recoil spring?Extractor looks to be in good shape and gets a good tight grip on the case. Ejector looks fine as well. Seems to happen randomly with all 3 mags. Any thoughts would be helpful,thanks. Pics to come.