Mismatched upper and lower headache.

[daddyusmaximus]

Didn't take me long to get in trouble on my newest build. Although I have built other (smaller .223/5.56) ARs, this is my first .308 build. I started it off last fall when I found a good deal on an bran new assembled CMMG MK3 lower for cheep in a private sale. I finally had some money for an upper, and decided that Areo Precision was getting good enough reviews to go with. It came in today, and looks very nicely done. The lines of both receivers fit up well, and there is very little play side to side. Everything is going fine... until I go to push the pins in. They are hard to get in and must be taped (firmly) in place.  I had to use a punch to get them back out and separate the two. The pivot pin hole in the upper looks perfect. there are no scratches inside the hole, though the pin seemed very tight. At the very top (12 o'clock) of the inside of the take down pin hole there is a scratch on the finish where the pin rubbed it's way through.

 

Is it possible to adjust the holes to fit? I was thinking I could sand a bit on the inside of the holes with a sand paper wrapped drill bit to open them up some.

I'm living off VA disability, so money is tight. I am not going to cheap out on the build. I will spring for quality parts, it's just that I will need time between each purchase, and I don't wish to have to go buy another lower if I can find a work around. It doesn't appear there is a need to adjust the fit of the two halves up or down, but I won't be sure of that until I can get a BCG and charging handle.

[blue109]

hate to say it, but CMMG is a four letter word around here of the profane sort! Quite a few issues lead back to their parts. All is not lost, and it might end up fine with a little massage work, but I'd wait to get it together to do anything permanent. It doesn't take much misalignment to run into bolt catch or feed issues.

[survivalshop]

  Consider your self lucky , there are lots of people that like them that tight . They may loosen up with break in rounds , might take a couple hundred rounds , but they will loosen a little when the Upper & lower seat from recoil  or because of the finish being worn off from using the Pin (s ) 

 Make sure they are clean & well oiled & check for Burr's .

[washguy]

Big Daddy   thats an ok thing...tight is right !   you said it was assembled?   hmmm im thinkin cmmg had bolt catch probs...you know if its a cmmg lpk?

     Wash

Edited April 30, 2016 by washguy

[daddyusmaximus]

The lower is a bran spanking new factory built complete MK3 lower. The guy had bought two of them, and didn't need both. I'm just excited to see the upper and lower together after the lower sat all winter in my gun cabinet. Should have barrel (Rainier Arms UltraMatch) and BCG (???) by the end of June.

 

Things getting busy though. I just got elected to be the next Post Commander at my VFW, and I take over in June. Trying to save the post, people are losing interest.  Did the flag, and led the Pledge at an Arbor Day thing today, met the mayor. Should be in the paper tomorrow.

[unforgiven]

Brother Don't beatup that lower and just sell it.I got the M5 Aero lower on thier sale for $275.00 assembled.Guys always run into problems trying to mix and match .308 AR parts from different manufactures.Not the same as the AR15 platform.Sadly.

[daddyusmaximus]

Can't buy anymore parts for a at least a couple weeks, but so far, all the places I've looked is sold out of the Aero M5 lower. Even if I have to go that route, not sure I want to sell the lower I have. I can always slap a CMMG upper on it and give it to my son. 

[unforgiven]

Good idea...

[Frankh252]

I have an Aero M5 upper & will soon see how she mates with a Juggernaut Tactical lower. Might toss some of the CMMG LPK items in the trash but will have to see what works first, since DPMS parts seem to have gone extinct.

[unforgiven]

These guys have everything :http://www.brownells.com/manufacturers/DPMS/index.htm hit the banner at the top to credit the forum.