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Posted: 5/13/2015 5:18:06 PM EDT
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Guys, I have a question.
I just assembled an Aero lower and put in my assembled Aero pistol upper. Everything works great, except the rear takedown pin sticks. The takedown pin slides through the lower (without upper installed) no problem. It sticks in the upper (when it is separated from the lower) unless I spin the takedown pin so its in the wrong orientation, if that makes sense. It's almost as if the hole in the upper is oblong. I tried two different takedown pins. I can tap the takedown pin all the way through with my plastic hammer but need a punch to tap the rear takedown pin out for disassembly. How do I fix this? Return the upper? Sand the takedown pin? Leave it? Here is the build: 
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| Came here looking for answers to the same problem I'm having today. Doing a 9mm build using a Spikes lower and RRA 9mm upper and it takes a mallet to close the rear take down pin! Takes a punch and hammer to open the damn thing up! Bushmaster, DPMS, S&W, uppers snap on and off...no problems. But, the RRA upper is tight as hell, and the rear take down pin won't come out without a punch and hammer. Was wondering if I should send the upper back, or just shoot the shit out of it after getting it built and hope it loosens up. Never had an upper and lower fit so damn tight and require tools to take down! |
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I had the same thing happen with my Aero lower and a BCM upper. After taking it apart several times its getting easier to push through. Just give it some time and it will be perfect.
Each manufacturer has tolerance specs for size and locations of each hole. They may be on the high or low end of some of the tolerances. Nothing to worry about 
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My 6.8 build was a small deadblow hammer fit. And back out again. Very tight. But - its loosening up. The next build was a pistol - and it rattles slightly. Loose.
That is an example of tolerances. The makers match them up best as they can to avoid it, we only get the ones we get and make do. Swap ten uppers onto one lower and you will find both extremes. Sort one hundred on the assembly line and you only ship good ones to please discerning customers. BUT - they ALL loosen up. |
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KTM: Like the other said, a tight takedown pin is normal. One of my ARs is equipped with an Accuwedge, to tighten the fit between the two receivers. To insert or remove the TD pin, I need to lean on the two halves to compress the wedge. Even then I sometimes have to use a plastic punch to drive the little bugger out.
I have another AR built with Mega receivers with a nylon-tipped screw in the lower that takes out all the slop between the two receivers. The TD pin on that rifle pushes in and out with finger pressure alone. In your case, you might try cleaning out the hole in the upper's lug with a brass bore brush, also lightly sand the pin itself to remove any high spots in the finish. A little bit of oil helps too. - CW |
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