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post #1 of 19 (permalink) Old 07-14-2010, 08:58 PM Thread Starter
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ar15 upper to lower problem

I have a complete cmmg lower receiver and trying to attach a complete dpms upper on it but the front pivot pin is hanging up on the upper and not fitting through. I pulled the front pivot pin and it fits fine in both the upper and lower and tested fitted them to see that looks like the lower cant go far enough to line the holes up entirely.

Anyone with any suggestions?
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post #2 of 19 (permalink) Old 07-15-2010, 10:19 AM
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I would take it to the AR-15 get together at Sonic's house this Friday. Those guys are AR-15 geniuses.




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post #3 of 19 (permalink) Old 07-15-2010, 10:32 AM Thread Starter
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I was thinking about it but idk if the distance/time frame will work out with my schedule as I'm in rowlett and have family to tend to.

It's very frustrating cause from looking at it the amount of the upper that doesn't line up it's a very small amount taking few thousandths of an inch.

I almost think if I could file a small bit of the flat of the pin it would go but I don't want to go there yet.
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post #4 of 19 (permalink) Old 07-15-2010, 10:43 AM
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Originally Posted by chevyhater01 View Post
I was thinking about it but idk if the distance/time frame will work out with my schedule as I'm in rowlett and have family to tend to.

It's very frustrating cause from looking at it the amount of the upper that doesn't line up it's a very small amount taking few thousandths of an inch.

I almost think if I could file a small bit of the flat of the pin it would go but I don't want to go there yet.
I was thinking this earlier but I didn't want to post it up. If you go that route I would take it slow.

Do you have pics of what you are talking about?

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post #5 of 19 (permalink) Old 07-15-2010, 10:44 AM
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Quote:
Originally Posted by chevyhater01 View Post
I was thinking about it but idk if the distance/time frame will work out with my schedule as I'm in rowlett and have family to tend to.

It's very frustrating cause from looking at it the amount of the upper that doesn't line up it's a very small amount taking few thousandths of an inch.

I almost think if I could file a small bit of the flat of the pin it would go but I don't want to go there yet.
Put your upper and lower together and light the hole in the front and see which receiver is binding. Do they mate flush? Any gaps? I would clamp them together and check the action for any interference. Do you have any other receivers you could swap parts onto?
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post #6 of 19 (permalink) Old 07-15-2010, 11:02 AM Thread Starter
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Put your upper and lower together and light the hole in the front and see which receiver is binding. Do they mate flush? Any gaps? I would clamp them together and check the action for any interference. Do you have any other receivers you could swap parts onto?
It had a cmmg upper on it that fit fine this dpms is a loaner the back will fit fine and it drops on perfect but the front pin won't fit. With the front pin out you can clearly see how the upper doesn't line up to the lower. I could take pics but it would be rather poor quality and don't think I could get the clarity needed.
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post #7 of 19 (permalink) Old 07-15-2010, 12:39 PM
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Quote:
Originally Posted by chevyhater01 View Post
I have a complete cmmg lower receiver and trying to attach a complete dpms upper on it but the front pivot pin is hanging up on the upper and not fitting through. I pulled the front pivot pin and it fits fine in both the upper and lower and tested fitted them to see that looks like the lower cant go far enough to line the holes up entirely.

Anyone with any suggestions?
Give it to me, I have a BFH.
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post #8 of 19 (permalink) Old 07-15-2010, 12:46 PM
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Has the upper ever worked on a lower before that you know of? I know you say it is a loaner. Have you ever had an upper on your CMMG that worked?

Can you pin the front then rotate the upper down to the rear and is it getting the same results?

If all fails Matt has a BFH.
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post #9 of 19 (permalink) Old 07-15-2010, 12:59 PM
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Originally Posted by sonic93 View Post
Has the upper ever worked on a lower before that you know of? I know you say it is a loaner. Have you ever had an upper on your CMMG that worked?

Can you pin the front then rotate the upper down to the rear and is it getting the same results?

If all fails Matt has a BFH.
It might just be a tight pin. I got a batch of Stag uppers that were very tight on the front pin. I used a rubber mallet to put them in, and a brass punch to work them out a couple of times, and they were fine. I can now take them off with my fingers.
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post #10 of 19 (permalink) Old 07-15-2010, 01:01 PM Thread Starter
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Yeah the upper came from a fully functional dpms rifle and the previous cmmg upper worked as well I cannot see any reason that this should not work. I'm stumped as for the obvious stuff and was hoping others could shed somelight before I file away. If there is someone close by to help I don't mind chipping in some gas money or pizza/beer.
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post #11 of 19 (permalink) Old 07-15-2010, 01:23 PM
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Originally Posted by 03trubluGT View Post
It might just be a tight pin. I got a batch of Stag uppers that were very tight on the front pin. I used a rubber mallet to put them in, and a brass punch to work them out a couple of times, and they were fine. I can now take them off with my fingers.

I have just the opposite with my pin. It's so loose it's a chore to keep pushing the danged thing back in. Was thinking about maybe putting a small burr on it...
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post #12 of 19 (permalink) Old 07-15-2010, 01:29 PM
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Originally Posted by chevyhater01 View Post
Yeah the upper came from a fully functional dpms rifle and the previous cmmg upper worked as well I cannot see any reason that this should not work. I'm stumped as for the obvious stuff and was hoping others could shed somelight before I file away. If there is someone close by to help I don't mind chipping in some gas money or pizza/beer.
With that said I am going to have to go with, tight pin. If you have a true punch you may be able to line it up. Similar to an awl would be great. Light taps to drive it once it is close. Lots of lube.
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post #13 of 19 (permalink) Old 07-15-2010, 01:31 PM
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Quote:
Originally Posted by chevyhater01 View Post
Yeah the upper came from a fully functional dpms rifle and the previous cmmg upper worked as well I cannot see any reason that this should not work. I'm stumped as for the obvious stuff and was hoping others could shed somelight before I file away. If there is someone close by to help I don't mind chipping in some gas money or pizza/beer.
It should work. I'm thinking it's a pin issue. Can you put the upper on the lower and look at the front hole to see how close it is?

Have you tried putting the lower on it and putting the front pin in first, and then lowering the rear to mate? Or putting the upper on the lower and putting the rear pin in first?
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post #14 of 19 (permalink) Old 07-15-2010, 02:04 PM Thread Starter
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Originally Posted by 03trubluGT View Post
It should work. I'm thinking it's a pin issue. Can you put the upper on the lower and look at the front hole to see how close it is?

Have you tried putting the lower on it and putting the front pin in first, and then lowering the rear to mate? Or putting the upper on the lower and putting the rear pin in first?
Yes I after my original try I pulled the front pin completely from the lower and set the upper down on it too check the alignment this is how I'm able to see the hole for upper is off.

I've been assembling the AR by trying to install the front pin first then set it down and push the back pin its a no go. So I tried to install the back pin first no issue go to install the front pin wont go in cause it hang's up on the upper.

I've tried to lube up the front pin to assist it still wont go as it's physically hitting the OD of the upper its even marked it from where I've tried to lightly tap it in.

As this is a borrowed upper I don't want to go hitting it and damaging the finish any further.

Like I've said as I know this should work and shouldn't be this hard as I never had issue's prior till installing this upper.

When I pulled the front pin I test fitted it in both the lower and upper and does not bind up and moves freely but once to fit the two together the holes don't line up enough for it to pass through.
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post #15 of 19 (permalink) Old 07-15-2010, 02:09 PM
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Tolerances should be MIL SPEC, so it should fit. Varying manufacturers might be a tad off, and if CMMG was a tad small and DPMS was a tad large, therefore maybe rendering this an impossible fit.

I would NOT file anything.
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post #16 of 19 (permalink) Old 07-15-2010, 03:23 PM Thread Starter
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Originally Posted by 03trubluGT View Post
Tolerances should be MIL SPEC, so it should fit. Varying manufacturers might be a tad off, and if CMMG was a tad small and DPMS was a tad large, therefore maybe rendering this an impossible fit.

I would NOT file anything.
Yeah at first I thought I had the dreaded big pin small pin mix up that's not the case I'm thinking your right on the stack up idea just don't know how I'm going to resolve it as I'm shopping for uppers right now and seems like I could run into this issue again on whatever I buy.
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post #17 of 19 (permalink) Old 07-15-2010, 03:29 PM
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I have just the opposite with my pin. It's so loose it's a chore to keep pushing the danged thing back in. Was thinking about maybe putting a small burr on it...

If you used a dpms parts kit this is why. They work but they are junk Imho. My rra pins fit like a champ. No slack and solid feel. My dmps kits always just feel exactly what they are cheap.

What you might call solitude is something i look forward to.
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post #18 of 19 (permalink) Old 07-15-2010, 04:20 PM
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If you used a dpms parts kit this is why. They work but they are junk Imho. My rra pins fit like a champ. No slack and solid feel. My dmps kits always just feel exactly what they are cheap.
Fuck. And I just got two DPMS LPKs.
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post #19 of 19 (permalink) Old 07-19-2010, 08:53 PM
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I have just the opposite with my pin. It's so loose it's a chore to keep pushing the danged thing back in. Was thinking about maybe putting a small burr on it...

Next time we meet up, bring it, I'll fix that for ya.



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