Had an interesting problem. Was practicing with my Glock 30 45acp and had a failure to extract. I did the normal tap, rack, assess drill and a few rounds later the slide jammed open. I had to hold the slide and whack the muzzle to get it unjammed. Manually cycled a few times and all was ok but the next round it jammed again. Figuring something was broken, I stripped it down and found no problem with the barrel or internals. Upon cleaning the barrel I noticed a slight gray ring about 0.1" in front of the chamber. I got out my micrometers and measured the barrel OD and found it had bulged about 0.004" in that spot, much to small to see or feel. I chucked the barrel into my lathe and took a 0.002" cut and now everything works fine. I have seen bulged barrels but never one with such a slight bulge that seems to have zero effect on performance and is such a mystery as to how it happened.