A number of years ago I picked up one of those Yugoslavian K98 mausers at a gun show. Not the prettiest thing in the world, but the price was good and I thought it was a reasonable deal since I like collecting old military firearms. I also bought some ammo that I was told was the correct caliber.
Well after shooting it a few times I realized that perhaps things weren't as they should be. It would chamber and shoot fine, but then the bolt was very stiff when I worked it to extract the spent casing.
I took it to one gunsmith who told me the head space was out. I was disappointed since my wife had actually bought the gun for me as a b-day present. So I just figured it would be a non-working memory of her good intentions.
That was several years ago, but I decided I wanted to investigate exactly what could be done to make the rifle usable, so I went to another smith today. He checked it out with his measuring dies and it looked OK. He examined the bolt and the chamber and could see nothing outwardly amiss. So he took it to the range and fired one round of new factory ammo as a final test, and it worked fine.
So the problem was apparently with the ammo I was using. Upon examination, it is Russian in origin, with 7.9 mm on the label, along with the numbers 38/51. The rest of the writing is Cyrillic, which means I haven't clue what it says. I wonder if the ammo is not the correct stuff, or as the smith said it could be that it was just so old that it had broken down and some nitro had separated out causing excessive pressure. It also has numbers 11-1952 on the label, but could that be the date of manufacture? Seems like they wouldn't necessarily use our dating system in that way.
Anyway I'm glad that the rifle is functioning properly. That's the important part. But I'm very curious about this weird ammo. Somebody out there might have some knowledge on the subject.
Addendum; found this on the 'net. Looks like that 11-1952 date might when it was manufactured... https://www.cdvs.us/product/8mm-maus...-15-round-box/
Given the unknown values of eastern block stuff at that time, it just might be way too old to be safely fired.