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Posted: 9/24/2013 4:57:47 AM EDT
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I am putting together my second M16A1 "clone". The first one went together without any issues, in particular the fit between the Tactical Machining lower and DPMS upper. I can break it down easily without any tools. The second build does not fit up so well. It is another new DPMS upper and an Aero Precision lower. The rear pin is very tight and cannot be manipulated using my fingers only. I realize most things in life are a combination of art and science, so what 'art' is recommended here to get the mating correct? As you can see from the picture, it seems a bit of material needs to be removed from the bottom surface of the rear hole on the upper to get the fit correct. Is this correct? If so what is the preferred method to do this. I am a newbie to ARs so do not worry about insulting my knowledge.
Thanks, Scott https://www.filesanywhere.com/FS/M.aspx?v=8c6a658d5c94a078a398 |
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The AP lower is probably slight out of spec. I had an AP lower that needed magwell dremeling to be able to insert a GI mag easily or have it drop free. Ended up selling it becuase I didn't want to mess with it.
As stated above I would just use a delrin punch to remove the pin and leave it as is, as long as it functions correctly (which it should). Some commercial variants are notoriously tight, such as early RRA rifles. If you start removing material from the upper and lower receivers you may create an obvious bubba fix that decreases resale value, and I have found they can loosen up a little upon firing a few hundred rounds. I have a rifle that is tight like that. If you did anything, I remove material from the rear pin and not the receivers. That is easy and cheap to replace, unlike the receivers. But then you stand a chance of eroding the rear pin hole if there is movement of the pin. Of course that might fix your tightness. But I would likely not do anything. Just my 2 cents. |
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Quoted:
The AP lower is probably slight out of spec. I had an AP lower that needed magwell dremeling to be able to insert a GI mag easily or have it drop free. Ended up selling it becuase I didn't want to mess with it. As stated above I would just use a delrin punch to remove the pin and leave it as is, as long as it functions correctly (which it should). Some commercial variants are notoriously tight, such as early RRA rifles. If you start removing material from the upper and lower receivers you may create an obvious bubba fix that decreases resale value, and I have found they can loosen up a little upon firing a few hundred rounds. I have a rifle that is tight like that. If you did anything, I remove material from the rear pin and not the receivers. That is easy and cheap to replace, unlike the receivers. But then you stand a chance of eroding the rear pin hole if there is movement of the pin. Of course that might fix your tightness. But I would likely not do anything. Just my 2 cents. What he said. I wouldn't touch it especially since your in Md cant buy a new lower in the state of Md after next Monday if anything were to happen from you taking off material. It will probably loose up over time. |
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It looks like the back of the upper is making contact with the buffer tower portion of the lower. If it is, then it may not allow it to go down far enough for your takedown pin to line up. Can you put the takedown pin through the upper and lower with the pivot pin removed? If you can, then that would be your problem.
If you can't push the takedown pin through the upper and lower with the pivot pin removed, use some gage pins to measure the size of the takedown hole on the upper and lower, then measure your takedown pin. You can use a .250" dowel pin or the shank of a straight 1/4" drill bit (stone down any burrs on the drill shank) if you don't have access to gage pins. If the .250" dowel pin or drill shank passes, then the holes in the upper and lower are big enough. Measure your takedown pin as well. As long as it's smaller than the takedown holes you should be good. I have a .248" diameter takedown pin I would trade you if your takedown pin measures larger than that. HTH |
| take a rat tail file to the uppers rear takedown hole (just run it accross the bottom of the hole a couple times and check it). i had one set that was real tight. a couple light passes and it fit like a glove, snug with no rattle but the takedown pin moved easily. just go real easy, it doesnt take much. |
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