I'm pretty sure that when I crushed my rivets into the larger than normal 74 trunnion holes, the rivets expanded to fit the holes. I mean they do expand when you crush them, so what's the issue?
I am not saying what you did would be wrong, they should be fine.
The Polish 74 tantal uses 6 standard swell neck rivets for its barrel trunnion. They designed it differently from their AKMs for some reason. Possibly the more violent, higher pressures associated from the 5.45x39mm round. I would assume the Bulgarians developed their rifles with the change to compensate for the different pressures associated with 74s too. They went with a larger sized rivet for 4 of the 6 rivets. Has anybody seen a Russian 74 trunnion with rivets removed, what are the hole sizes? Add to the mix why are the more modern Russian and Bulgys using two rivet bullet guides over the previous one rivet?
The available factory Bulgarian rivets are 4 larger swell necks and it includes the flat head rivet for the Arsenal FCG anti-trigger slap feature too. That would be what Arsenal in Bulgaria would use for assembling their 74s.
Rivets by design are supposed to be expanded only so much to maintain designed specifications.
I found some pics I did before covering the same topic.
Romy G uses 4 standards, 2 standard swell necks.
Bulgy 74s uses 4 larger swell necks, 2 standards.
Polish Tantal 74 uses 6 standard swell necks.
Top to bottom Romy, Bulgy and Polish Tantal
Left to Right Romy, Bulgy, and Polish Tantal
I hope you can see the difference in the pictures. :smile: