Old rifle and old ammo = misfire
I'm trying to figure out what exactly happened, so I figured I'd see if anyone here has some ideas.
Background: I have a K43 in 8mm my grandfather brought back from WW2. He gave it to me with a cracked extractor and missing retaining screw/spring. I've since replaced the parts. I've also acquired some old ammo (dated 1989) to use with it. It's mainly a safe queen, but I decided to hit the range with my camera and send my grandfather some pictures of the "restored" rifle.
I loaded 8 rounds in the mag and began firing slowly. I worked through 6 rounds, and the sixth failed to cycle the action. Smoke poured out the back of the action, and then near the chamber. It stopped smoking just as quickly. I couldn't cycle the action, and had to gently persuade it once I got home. The round that came out looked intact, bullet seated, but the primer was pushed in a bit and the firing pin had left it's mark. The fact that it was resisting coming out of the chamber makes me think the case had bulged, but I couldn't see anything to that effect.
Now, I've had revolver rounds fail to fire, but the primer only puts out a little smoke. I assume the same thing happened here, but the smoke coming from 2 locations and the amount of it just kinda threw me. I could hear some powder still in the rounds case. The rifle appears to be fine, chamber clean and cycles rounds again.
Is the primer just that much bigger on an 8mm, or did something else happen? I hate not knowing.