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Long time lurker, finally made an account to adress this question.

AKartwheel

Plastic
Joined
Jul 29, 2020
This is for an akm pattern rifle, the question is how would one properly and correctly fix a barrel pin hole in the trunnion that out spec/roundness beyond it's maximum allowable tolerance? How could something like this be welded/add material to a hole where an average welder is too big to reach in a hole as small and deep as this one? I'm sure there is a correct way to doing this, on akfiles people just say it's junk if it's too far out of size. Any idea's? Thanks.


Example of what I'm talking about, it's 1" deep.
20140210_080052.jpg
 
Can you ream it out and just use a bigger pin ?
Don


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eKretz I thought about sleeving before, however the sleeve might have complication being the cut to make room for the pin channel in the barrel.
Example:
004_zpse529573c.jpg


Yes that's usually what people do, however the hole is a .275" and the largest people go is .315". Now if you're above .315 people usually look at the trunnion as not usable being the hole will punch through the recessed portion of the trunnion where the rear sight block mates to.

Example:
IMG_9455.jpg
 
Yes I see there isn't much wall there on the one corner. You could always offset the sleeve/plug, then put the actual hole back in the correct place. Cutting away the part of the sleeve/plug that goes through the larger bore should be easy enough. After the mating part is installed it will help hold the partial sleeve in place.
 
Yes I see there isn't much wall there on the one corner. You could always offset the sleeve/plug, then put the actual hole back in the correct place. Cutting away the part of the sleeve/plug that goes through the larger bore should be easy enough. After the mating part is installed it will help hold the partial sleeve in place.

The thing about the barrel pin to itself is supposed to be a .003" press fit. I'd imagine I could tig weld the outer sleeve, however this repair starts to seem to be getting murky again.
 
Here at the small town machine shop I work at, we get in a lot of work consisting of worn out pins and/or holes. This is a tough one, because the wall thickness is so thin. If it is not a high stress area, I would section out that portion that has the hole. Then build a matching piece, TIG it in place, and drill that. The matching piece could be gotten out of another part that has the correct hole already, but matching locations exactly adds a bit more of a challenge.
 
It isn't considered good gunsmithing practice to be welding on a heat treated receiver where it is stressed. Welding changes the metal's structure and the hardness.
Your trunnion block with hole and pin is the equivalent to that.

It has been ruined and you are risking catastrophic failure by attempting to salvage it.
 
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According to the engineers at Arsenal in Bulgaria, these receivers were never designed to be re-barreled. When the barrel is shot out, 10-15,000 rounds, the receiver has stretched and worn to the point of failure on the next barrel. The installation of the initial barrel is done with a press, similar to a log splitter, this expands and stresses the metal. A replacement barrel would have to have an oversize tenon to work properly, and that would then stress the metal more. The pin hole you are trying to repair is drilled after the barrel is installed, drilling both the receiver and the barrel. Having watched the entire fabrication process and met with the engineers, the rebuilding of AK type rifles is doable but not recommended and will have many issues to overcome
 
Bore it, sleeve it, silver solder the sleeve. Or pitch it in the dust bin. It's not a collectors item.
 








 
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