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Old July 28, 2013, 10:52 PM   #1
Metal god
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Does loose AR receiver mating hurt accuracy ?

I always thought if your receivers were sloppy or loose it could hurt accuracy . I would think if the barrel moved before the bullet leaves the barrel it would hurt POI . A right up from Armalite says different and there is no accuracy issues and the bullet leaves the barrel before any real movement occurs .

Here is what they said in 2003
http://www.armalite.com/images/Tech%...0Tightness.pdf

Does anybody know where to find the data from the 1970s testing they referenced ?

Things I'd like to know and if youguys think this would matter

1) I'd like to see is if they did the test out to 1000yds and what was the accuracy tolerances . Was it 4moa or was sub moa they were looking for? If they were excepting 4moa as accurate , as mil-spec excepts . They would never see if there was a difference ?

2) Did they use match ammo and did they lock the lower in a vice ?

3)Did they use a loose fitting upper in a vised lower then clamp a lower and upper together so to be sure there was no movement and compare the two ? or were they just comparing random receivers that we know they make well and the fit would have been good anyways ?

I'd like to know how scientific the test really was .

Last edited by Metal god; July 29, 2013 at 01:42 AM.
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Old July 29, 2013, 12:10 AM   #2
Auto426
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No, it does not affect the mechanical accuracy of an AR. The barrel is fixed to the upper receiver, and the sights are fixed to the upper receiver and the barrel (unless someone is running a low-pro gas block with a backup on the hand guard). The bolt locks into the barrel extension, also in the upper receiver. The lower receiver is really just a gun mount. All of the parts that affect the mechanical accuracy of the rifle are fixed to the upper.

Now, if an AR has a really loose fit between the upper and lower that may throw off the accuracy of the shooter. A wobbly rifle isn't as easy to get repeat accurate shots with as one that's rock solid, but it would take a very loose upper and lower to make a noticeable difference in most people's offhand shooting.
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Old July 29, 2013, 01:03 AM   #3
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As Auto said certain amounts of looseness won't affect the accuracy (unless it becomes severe enough as to affect followup shots). If I find a lower and upper that are too lose I install ( http://www.armalite.com/ItemForm.asp...d-8a3c238a7007 ).
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Old July 29, 2013, 01:13 AM   #4
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I trust what ArmaLite says here even though I haven't seen that 1970 study. As long as the upper flops back to the same location after every shot, accuracy should be within factory specs for that model with ammo it likes.

One way to find out: get groupings from a loose fitting upper/lower then try again with an accuwedge.
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Old July 29, 2013, 01:55 AM   #5
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I get what you all are saying . Here is what keeps bothering me about this . Unlike many if not most other rifles the AR has a pivot point where the two receivers are attached . For lack of a better term , I see the rifle buckle/pivot/slide in the middle of the rifle under recoil . Thats where I see the possible inconsistencies of POI coming from . To me it would be like saying it's OK to have the screws that attatch your stock to your bolt action receiver just a little loose . That will not cause accuracy issues . I don't think any of us would say that would be OK so why is it no big deal on a AR ?
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Old July 29, 2013, 07:04 AM   #6
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FWIW; maybe not germane: I bought a 700 Ti. Mounted a scope, sighted it in. Decided to adjust the trigger. Discovered that the receiver screws were at about a dozen inch-pounds, not the specified sixty. After adjusting and reassembling, I went back to the bench rest.

Not only same group size, but same point of impact.

Sorta flies in the face of conventional wisdom. It certainly startled me.
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Old July 29, 2013, 07:22 AM   #7
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The effect is probably not noticeable and falls within the normal accuracy parameters. If there's enough "slop", it may affect feeding but that would be extreme. If the amount of movement bothers you, put one of the little rubber thingies under the takedown pin to put tension on the assembly.
I see quite a few different upper vs. lower inconsistencies but usually it's in the "too tight" direction. I helped my older Son assemble a lower yesterday and since it had been a while since I'd put one together(I'll blame it on that anyway) I failed to check the upper to lower fit before starting. Sure enough when we were finished, the upper to lower fit was much too tight for my satisfaction. We ended up swapping his fire control parts to another lower(which I checked for fit BEFORE starting). Same lower brands(different production run) and same upper but enough interference to make pushing the pins unreasonably difficult.
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Old August 1, 2013, 09:09 PM   #8
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One of the reasons HK uses the roller pins it uses in its AR's is to ensure a tight, consistent upper to lower fit to improve accuracy.
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Old August 1, 2013, 10:47 PM   #9
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One other cheaper option for tightening up the upper to lower is to install an "acu-wedge" Cheap rubber wedge that sits in the rear of the lower and engages the rear lug of the upper as you close the two.

http://www.cheaperthandirt.com/product/ARR-006
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Old August 2, 2013, 08:16 AM   #10
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Quote:
One other cheaper option for tightening up the upper to lower is to install an "acu-wedge" Cheap rubber wedge that sits in the rear of the lower and engages the rear lug of the upper as you close the two.

http://www.cheaperthandirt.com/product/ARR-006
Yes, but please don't spend $9.97 for one from CTD. A reputable business will sell you an Accu-wedge for about 3 bucks.
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Old August 2, 2013, 03:12 PM   #11
Metal god
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Yes CTD can blankitty blank blank blank . FWIW I do not have any issues with the way any of my ARs fit . I was just asking the question .
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Old August 2, 2013, 05:37 PM   #12
fileophile
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different opinions...

on whether the lose fit matters. To me it does, and if the fit is loose I will "bed" it with epoxy to firm it up. (Check the internet for the procedure -- it took me only about 5 - 10 minutes plus drying time.)
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Old August 2, 2013, 06:43 PM   #13
Coach Z
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Calm down guys the $10 was for a three pack, fair market price! They just happened to be the first seller that came up when I searched accuwedge that's all, not pushing one seller over another.
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Old August 2, 2013, 09:52 PM   #14
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Quote:
Calm down guys the $10 was for a three pack, fair market price! They just happened to be the first seller that came up when I searched accuwedge that's all, not pushing one seller over another.
I still stand by my comment not to buy from CTD.
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Old August 2, 2013, 10:34 PM   #15
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ME TOO ^^^ I will not even go to there website . Coachz no problem this ain't on you man it's all on CTD . I am very serious about not using them . I was at a friends house the other day and he was about to order from them and I went ballistic ( really ) He thought I was kidding at first but it became very clear I was not . I went on a five minute rant about those guys till he closed out the tab . WOW just thinking about them gets me all worked up , Grrrrrr .
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Old August 3, 2013, 10:38 AM   #16
Art Eatman
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More than enough about CTD.
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Old August 3, 2013, 10:45 AM   #17
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I've had a number of AR's over the years. Some uppers and lowers locked up tightly, some not. My conclusion after many rounds is that with an AR accuracy is with the barrel and the load. The lower has little to do with anything other than holding the mag and the trigger. A good trigger makes a difference but a sloppy lock up does not.
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Old August 3, 2013, 11:15 AM   #18
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A bud of mine was listed by the NRA as one of the top 200 highpower shooters in the US. He used a AR15 space gun.

We talked about this issue, whether the upper and lower needed to be tight, and as a demonstartion Bud handed me his rifle. His lower moved in an arc around the upper.

I like a tight upper and lower because the movement just bothers me. Does not mean a thing for accuracy.

On bolt rifles, Garands/M1a's it is different.
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Old August 3, 2013, 01:50 PM   #19
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I put a rubber O ring on the front pin post on my receiver and it eliminated all play.
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Old August 4, 2013, 09:24 AM   #20
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I've got a Colt 6920 and the upper and lower have a lot of play between them. At 100 yards I haven't seen accuracy issues. I also have a S&W M&P15and its considerably tighter when it comes to the receivers mating up. At 100 yards it does not seem to shoot any better than the Colt.

If the wobble bothers you get a Accuwedge or JP Enterprises rear tensioning pin.
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Old August 5, 2013, 11:21 AM   #21
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Critical parts of the gun are just as accurate whether the fit between upper and lower is sloppy or snug. Distractions & inconsistencies with relation to the shooter can play a factor due to movement there, however.
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Old August 7, 2013, 08:16 AM   #22
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You should see my issued M4...that thing rattles like crazy, but it doesn't have any accuracy problems. Then again, the furthest we shoot is 500 yeards, but the target is just a human silhouette.
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