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Discussion Starter · #1 ·
Working on a Federal Arms FA91 for a guy, the pins are solid up front, no front trunion movement yet. I am not a gunsmith but have built dozens of AK's from kits, several bolt guns and 1919A4's and am an amature machinist. I have determined that this gun has excessive charging handle gap and will not unlock without a screwdriver to finish opening the bolt gap from the bottom first. But I think I have all the info to procede with the gap checks, bolt and charging handle, and repair.
My question is: When I dissassembled the gun I found evidence of the bolt and carrier slammming back into the rear stock trunion with enough force to bend both the pins, drive the steel cupped area of the stock end back about 1/8" and drive the stock out of the pocket pulling the screw socket inserts out of the stock. The owner said he lost a roller retainer about a year ago and the rifle would not function, he had it repaired by a gunsmith that has since closed up shop. He said the rifle fired fine after and only recently would not charge. Am I looking at weak recoil spring? Hot loads? Rollers not fully locking? Headspace issues? Anyone seen this type of damage before?
The owner is 69 and isn't very helpful when I ask questions, he just says it's damn accurate when it shoots.
He did supply some ammo for testing and it is some old European looking stuff with what looks to be a nickel colored bullet several headstamp markings and a 63 date stamp.
 

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My question is: When I dissassembled the gun I found evidence of the bolt and carrier slammming back into the rear stock trunion with enough force to bend both the pins, drive the steel cupped area of the stock end back about 1/8" and drive the stock out of the pocket pulling the screw socket inserts out of the stock. The owner said he lost a roller retainer about a year ago and the rifle would not function, he had it repaired by a gunsmith that has since closed up shop. He said the rifle fired fine after and only recently would not charge. Am I looking at weak recoil spring? Hot loads? Rollers not fully locking? Headspace issues? Anyone seen this type of damage before?
Sounds like the rifle is over functioning.

Check bolt gap & roller size.

Check the locking piece is appropriate for the gun.

These FA91 guns have a limited lifespan will eventually self disassemble when the steel trunion separates from the receiver... this may be what is happening.

Really the right fix for this gun is to move all the parts to a new steel receiver. The FA91's are known-bad and there is mostly nothing you can to correct the problem
 

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Discussion Starter · #3 ·
Trunion is still solid, but pretty much everything else is loose or out of tolerance. I will check the mentioned items once I visit the FAQ some more to understand how it all works together.
The scary thing is that the recoil issue isn't what he brought it in for, just the not charging problem.
 

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I've got a Springfield rifle which is basically the same as the FA91.
I have that same issue with excessive gap in the cocking tube such that the charging handle doesn't properly cam open the bolt.
The problem is the cocking tube is welded to the front site triple tree, so the problem gets worse as the gun gets hot.
I seam to remember that the FAC guns might have it attached differently with glue or something in the receiver, which isn't going to hold up anyway.
Take the bayo plug or dust cover off the front sight, and look down the center of the hole in the triple tree tree to see if the cocking tube is welded to the inside of the triple tree, or maybe the outside of it. It it isn't attached in any way at the front, its probably glued, epoxied, pinned, whatever (but not welded) into the receiver at the rear of the cocking tube. As so, it probably worked loose over time, or if your heaspace decreased, then the carrier going further forward might have pushed the cocking tube forward. There is no good fix for that. One of the problems with that aluminum receiver design, the tube is meant to be welded to the receiver.
As far as the recoil problem: headspace, recoil spring, buffer. Who knows what the previous smith did, so start from square 1 and check it all.
As others have said, the only way to make the gun right is to move all the parts to a steel receiver. Most of the those guns were built with nice FMP parts that would make a great gun when rebuilt.
 
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