I've fired something like 500+ rounds through my WASR 10-63 without problem. A few days ago I was shooting the usual Tulammo 122 from bench and bags sighting in a scope. On the third set of five rounds I pulled the trigger, felt the engaging surfaces part, but no hammer fall. I knew I had rounds remaining. Pulling the charging handle a live round extracted from the chamber with not a scratch on the primer surface. It never happened again. Only thing I can think of is a round developed a little less oomph, the bolt came back far enough to extract, eject, and pick up and chamber the next round but not far enough back to cock the hammer. Thoughts? Thanks.

The hammer is cocked before the bolt moves back far enought to eject the fired case. You can pop off the dust cover, remove the recoil spring, and cycle the action by hand. The hammer is already under the sear before the ejector is through the bolt face.

I think it's much more likely that the real problem was the hammer following the bolt carrier down.

AJ