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Posted: 8/19/2015 10:25:13 AM EDT
| I have a stripped upper receiver on which the notch for the barrel pin is enlarged, allowing the barrel to rotate a few degrees... is it possible to fix and save this upper receiver, possibly either with shims and/or peening the threads around the notch??? |
| Did you purchase it new Or used? What manufacturer/vender? As a non transfer item I would explore an exchange first. If I had to do it , I would find a small piece of steel tubing and make a sleeve/bushing to fit snugly around the pin then file the sides until it fit the notch snugly. I know it's a tiny tiny custom part , but that's what I would do. |
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You should only need to put a bit of material on the side of the notch that was affected to prevent the barrel from rotating while tightening the barrel nut. It would seem some of the knead-to-mix clay type epoxy would work fine for this since it only needs to resist the rotation once. I would put a dab of grease on the barrel and insert it into the upper and rotate it opposite of the tightening direction of the barrel nut ( so to the right when looking at it from the top). spray some light oil onto the area to prevent sticking of the epoxy (think "Pam") and then mix up a little piece of the epoxy "clay" and put it on the left side of the pin down in the notch. Rotate the barrel until it's perfectly upright. Gently remove excess epoxy that is in or above the threads and leave it alone long enough for the epoxy to harden. Once it's hard you can put the barrel nut on over the epoxy as it will serve as your repair. Total cost, about $7.
I've used that stuff to make some really durable repairs to other things, and for this purpose it should certainly work. |
| Assuming it's enlarged to the driver side, try putting the barrel in a vise and maintaining counter clockwise (from rear) pressure on the receiver while torquing the barrel nut. Might mean putting a pair of vise grips on the upper pin block or clam shell, but that's what I'd do. I've had to deliberately enlarge the notch to compensate for slightly off (like 3° or less) FSBs before, never needed to shim the pin to maintain alignment while torquing. As long as your feed ramps and gas port align OK, you're GTG. |
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