Loose upper

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11 years 9 months ago #16143 by pjogrinc
Loose upper was created by pjogrinc
Just picked up a used AR-10 upper assembly. Armalite non-forward assist upper, Noveske gas block,tube and match forearm, Rock Creek 26 inch 5 groove barrel (have yet to determine if 5R, although probably not).

When it's mounted on my Armalite AR-10NM lower, the front hinge pin is a little loose.

My question is:
1. Should I worry about it and consider tightening up the upper reciever pivot pin?
2. Ream out pivot pin hole, insert a piece of SS and then ream to proper size hole?
3. Go gorrilla and peen the pivot pin hole sides and then reem to the correct size?

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11 years 9 months ago #16147 by Charlie
Replied by Charlie on topic Loose upper
I think I'd start by asking the "Dreaded Previous Owner" why it's loose.

Charlie

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11 years 9 months ago #16148 by pjogrinc
Replied by pjogrinc on topic Loose upper
Fits his fine, but the barrel work and other parts were done at Noveske a long time ago. His new upper assembly fits super tight. He had to hammer the pin in, but he has not taken it apart since he put the new upper on. Infact, you have to break the 2 halfs apart over your knee. Wonder if they stuck an oversized pin in when Noveske first set this up for match shooting??

It is no looser than the ones we used in the USAF, but for a match setup, you would think it would be tighter.

When I first talked to him about it, I was going to carbinerize the barrel and open up the gas port to get it to operate. But the more I learned about the pieces, that idea went out the window. For the price I paid, it was a very good deal.

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11 years 9 months ago #16150 by LebbenB
Replied by LebbenB on topic Loose upper
Could you define, "A little loose?" Is it merely easy to push in and out or does it vibrate loose from firing?

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11 years 9 months ago #16161 by Charlie
Replied by Charlie on topic Loose upper
There was an issue with people using M-16 uppers on AR-15 lowers which was that the M-16 used a 0.250 pin and Colt AR-15s used a 5/16" pin. I'm not saying that's the problem, but I'm wondering if Noveske uses a 5/16" and Armalite uses 0.250".

Have you got a micrometer?

Charlie

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11 years 9 months ago - 11 years 9 months ago #16188 by pjogrinc
Replied by pjogrinc on topic Loose upper
Front to back movement - can only force a 0.002 feeler gauge between back of upper and outer frame of lower by the recoil tube.
Side to side play - can rock the upper so I can force a .005 feeler gauge in.
The upper on my Armalite NM does not move at all.
This slop on the used upper might be a non issue. I shoot mostly bolt guns for paper punching, so I'm not use to any slop.

Reason this may be a non issue is that I fired it today at the range in 25F temperature. Fully bagged the gun off of the bench and using Sierra 155 Palma, 168 HPBT Match and 175 HPBT Match, all 5 shot groups could be covered with a quarter except for 1. Best 5 round group could easily be covered with a dime and the worst group was slightly bigger than the diameter of a quarter. Range was 100 yds. Barrel definetely shows a preference for the 155 Palma's. It would consistantly group the 155's into a nickel size group.

Definetely not 5/16 pins.
Last edit: 11 years 9 months ago by pjogrinc.

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11 years 9 months ago #16242 by BUILDING MY SASS
Replied by BUILDING MY SASS on topic Loose upper
Just my :twocents:

I just pulled my A4 C out and checked it...I have about the same movement and mine is a Pre forward asst...(the last year they made them)...you say that when it is on his lower there is no movement...it could be that it was mated to that lower...and his new upper fits very tight, this also leads me to believe that that upper was mated to that lower...as you said your NM upper has no movement at all..that is because the upper and lower are Mated to be an exact fit. Though most parts, upper and lowers, are interchangeable, there will always be some differences in fit and in some cases (that I have heard of) some parts just won't match up with some alterations....
All in all, I wouldn't worry about it, you said your groups are very good and have no issues with the pins coming loose, so I would say as long as if functions to your expectations...and nothing is coming loose...
Just go with it...
Again..just my :twocents:
BMS

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11 years 9 months ago #16243 by pjogrinc
Replied by pjogrinc on topic Loose upper
Ya, nothing comes loose from shooting.

Targets were good, but not exceptional. I know I can do better! Now, just have to warm up a bit, like to 45 or better to do some serious testing. For the mean time, it's back to the NM upper it came.

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