1 Mystery Bullet

We read about sticky issues and action problems that are hard to isolate. I just finished-up a lengthy hunt for a problem that had me cornered. I was fitting a spare bolt to a shooter and loaded-up a mag full of live ammo. Took it outside and cycled them thru by hand just to see how things felt. Upon cycling a mag, the bolt locked-up on the last round. I reloaded the mag, tried again and the bolt locked up about 5-down. Head-scratching commences. I grab a few more magazines and the problem randomly persisted on any mag. I change bolts which did not solve the problem. The light bulb came on in my head and I started considering the ammo. I was able to identify one round that was causing the problem. Every time it chambered, it would lock the bolt and required a serious karate-chop on the slide to rotate and unlock. No matter how hard I looked or measured, I could not detect any issue with it. This is exactly the sort of thing that can cause a cracked bolt. The round would feed, chamber, rotate and lock, but would not rotate and extract by hand.

Maybe your odd round is out-of-round in some way? Try measuring both the minimum and maximum diameter of the cartridge at a couple of different points along its length. Perhaps it got stepped on at some point in its life