9mm 124gr FMJs over about 4.5gr of Unique, and I THOUGHT I had my progressive press running like a clock. At the range, I fired, got distracted and didn't notice whether or not I hit the target at 50 yards, so I fired again. Blew the bolt catch off, bent the ejection port cover pin, scared the living crap out of me. It took a LOT of pounding on a set of GI cleaning rods to knock those two bullets out of the barrel. There is NO damage to the barrel, though I changed out the upper because on inspection it got bulged where the ejection port cover pin was bent.
The bullet on the left was on top, the one on the right was on the bottom.
I went through the rest of that batch and weighed each round. Almost all were within about .6 grains of each other, but a few were several grains light, so I pulled them all, starting with the light ones. Of the 5 I knew were light, only one had more than a few flakes of powder, and that one was about a 1/2 charge. I immediately ordered a powder check die for my progressive press, and I've used it ever since.