[tunabreath]

I have absolutely no idea what could be causing this. Occasionally, when firing in long-ish full auto bursts, the slide will get stuck back. It's not due to the slide catch, and usually only occurs if I started with a freshly gassed long mag (which has been allowed to warm up). It feels like there's just a lot of friction between the slide and the frame when it happens, and removing the magazine has no effect. Gently forcing the slide back forwards seems to correct the problem entirely until the next occurrence.

I can't think of anything that would do this. Is it a lube problem? That would coincide with the rough friction feeling, but I've lubed it pretty recently...

Edit:
Ok, it only seems to happen with one of my mags. The friction point seems to be between the back of the outer barrel and the top of the slide, behind the opening for the compensator. I think that something with this mag causes the recoil rod or outer barrel to be jarred out of place when fired on full auto, then returned to the correct position when I force it back into battery. I still have no idea how to prevent it though.
I've been using propane.