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Posted: 1/19/2016 10:30:23 PM EDT
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Hi,
So I am building an AR with a PSA lower and DD MK18 upper (sbr). I got the lower put together, but I have the problem of the upper/lower not going together easy. I can put the front pivot pin through the upper easy enough, but in order to get the back takedown pin to go through I have to a) tightly hold the lower/upper together while using a small brass hammer to tap the pin in (otherwise it would not go in by hand, unlike any of my other ARs). If I put the back pin in first, and then try to put the front pivot pin in, even with the aid of tools I cannot get it to go through. I tried putting my upper on another lower and it dropped right on. Similarly, when I put another upper on my PSA lower it drops right on. So I can get this DD upper to pin on my PSA lower if I do the front pivot pin first, using elbow grease and tapping the rear pin to get it to fit. Should I just leave it at that and try breaking it in with some rounds? The part that confused me the most is that the only issue is fitting these 2 specific parts together, but when I use one of them with another upper/lower they drop on just fine. |
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It happens. You get a little bit of tolerance stacking or something slightly out of spec between manufacturers and you get a really tight fit. I've had the same issue on a couple of different ARs, one of them a billet set.
Yep, as long as everything functions properly, just go ahead and shoot it. It will likely loosen up some over time. |
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Quoted: It happens. You get a little bit of tolerance stacking or something slightly out of spec between manufacturers and you get a really tight fit. I've had the same issue on a couple of different ARs, one of them a billet set. Yep, as long as everything functions properly, just go ahead and shoot it. It will likely loosen up some over time. |
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I started a thread recently because I had the same issue. Mine required a very small amount of material removed to solve the problem. It was tight enough that I don't think it would have cured itself just by putting some ammo through it, but one never knows. http://www.ar15.com/forums/t_3_4/687545_Takedown_Pin_Reamer__Which_type_.html |
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