I had long believed that some AKs had the barrel an trunion installed in the receiver as assemble an not first the trunion in the receiver an then installing the barrel .
My very first build was doen with rivets an I bucked the backs on the barrel . Guys claimed this was the wrong way to do it an you cant see if the rivet is loose or not . Well guess what! here is a video of a Polish AK marker setting rivets on the barrel. BTW my original build has about 6000 rounds on it an is still tight .
Pioneer Arms Corp
The old AGI video used to show doing them almost the dame way . but with a hammer an they split the ends to make them spread better .
I don't know if pioneer makes military rifles or how big they are but here is proof that at least one manufacture does it as I have long suspected. the trunion is pressed on the barrel an head spaced first then installed in the receiver .
they use a separate tool to press the rivets by the mag well .