Which came first...the chicken or the egg? Was this firing pin hole big to start with, or did flame-cutting via a perforated primer create the cavity? Note the two bolts. The one on the right is normal, the one on the left has a hole large enough to poke a nail thru. (Pay no attention to the pills and spent brass...they are not part of the story.)

The subject carbine is an Iver Johnson and both bolts are commercial. I shoot this carbine on a somewhat regular basis. Took it out yesterday afternoon and...thud. Nothing would fire due to very light primer strikes. I fooled with it for a while and detected nothing amiss, but it still would not fire. I replaced the firing pin and hammer, tried again and it went bang every time. I always check my fired brass and when I looked at this handful, 2 had perforated primers and I mean a clear hole all the way thru. When I dissembled the bolt I noticed the enlarged firing pin hole. From what I could detect, I only had the two perforated primers.

I replaced the bolt, assembled the carbine and it runs just fine. I am wondering if the hole has always been large contributing to the light strikes, or just a couple of perforated primers was all it took to flame-cut the opening?

The carbine runs fine now and I never did discover an issue causing the light strikes in the first place.

For clarity: are these 2 different types of commercial bolts? the cut for the extractor plunger area looks different. then there is the extra slot opposite the extractor plunger hole on the on on the right.

Stick the shaft of a drill bit in the hole, is it concentric? I would think if done by primers the hole would not be round or conical.

Is it possible that there was a commercial firing pin that has a wider area just behind the pin?

Here is a firing pin that I believe to be a commercial pin and not a Winchester made as the marking would suggest

I only used the 9mm bolt to compare firing pin holes. The 9mm bolts take the same internals as the 30’s, except for the extractor.

The firing pin in the carbine at the time is still dimensionally the same as other GI pins I have and the nose looks perfect.

I think something was happening at the back of the bolt with the hammer, but I can’t see it. 

The enlarged hole in the damaged bolt is perfectly round, looks like it was drilled-out.

The pocket is surely too deep now. I did not find any debris in the pin-channel or on the pin. The front half of the pin is severely discolored from the blast. Whatever went wherever was vaporized. This was a used bolt from a parts-lot, so I have no idea what it’s been in. I am sure I had fired maybe 100 rounds thru it before this occurred.

GI Spec for FP Protrusion:

Max - 0.065

Min -  0.048

Any signs of the Extractors stem or Firing Pins mating groove showing excess wear ?

Nothing out of the ordinary. I am shooting the carbine now with the same bolt internals, just another bolt.