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Posted: 7/25/2014 2:05:43 PM EDT
Just completed my first lower build yesterday
and went to mate it up with a PSA 20 inch upper. Everything was going good until I tried to push in the rear take-down pin. It fit 3/4 of the way through and stopped. 
In all my wonderful judgement I tapped the pin in with a brass hammer. 
Now the pin takes a punch to pound out if I want to disassemble. Is this something that will "wear in" over time, or do I need to mill out the hole in the upper a little? 
And for informational purposes, the pin slides in and out with ease in the lower when separated from the upper. Idid notice some wear on the bottom of the takedown pin where it is binding, and in the hole for the upper.Any help would be appreciated. 
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See if it does the same thing with other uppers. I discovered that some upper receivers have a slight shoulder on the base of the tower that slides into the lower where the rear takedown pin goes. If you can mill/file out the lower pocket a bit to accommodate the shoulder on the upper tower, it should ease the resistance on the pin going thru.
I ran into this problem when doing 80% lowers. Had to take a bit more material off to accommodate the shoulder, then the pin was snug, but I didn't have to beat it in and out. |
| This is a good problem, you don't want loose tolerances that cause the upper to wobble. Like others have said, shoot it and shoot it some more. It will get easier to punch out the more you shoot and clean it, people that have loose fitting receivers buy accuwedges to tighten up their receivers. |
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Quoted:
Yeah tight is good except The more its pushed in and out it works the aluminum and not the easy to change pin Tune on the pin before you egg out the holes in the aluminum. Bingo!!! Always work the cheapest part first! Secind from the look of the pin there is a massive burr or ledge in the rear takedown of the upper!!! Quick fix is take some 600 grit wet dry and cut a little strip and tape it to a drill bit or mandrel and just LIGHTLY polish it up!! I work on guns for a living and I will be willing to bet that is the problem. If it isnt check the lower reciever rear takedown holes for burrs and ridges and work them as necessary. Be very very careful with your work!!!! Hope this helps a bit. |
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