Matching upper and lower receivers.

[ChunkyMonkey]

Virtually every AR15 I have ever touched has that annoying looseness between the lower and upper. Found a great article addressing this issue and the explanation put the problem as plus mill spec and minus mill spec. That is if the upper leans more to one side of the acceptable tolerance and the matching lower leans in the opposite direction for tolerance you can end up with sloppy fit (not tight).

Would that suggest we should buy matched upper and lowers as a combination only?


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Have you shot anything milspec? They make more noise than a cornered rattle snake. If it works and it shoots straight.. dont worry about it.

[porterdavid98]

Have you shot anything milspec? They make more noise than a cornered rattle snake. If it works and it shoots straight.. dont worry about it.

Thanks for your insight. Yep, no doubt sloppy loose is normal. And yes, I agree what happens under the upper receiver has very little to do with the accuracy of a chambered round. So yes, I have shot many milspec AR's. So now I will ask you a question. Have you ever held or shot a "accurized" AR? There is no slop or looseness. How long will it stay that way? I have no idea, but it is great while it last.

Regarding accuwedge and "O" rings or shims, I agree, these are bandaids not fixes.


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[Great-Kazoo]

Thanks for your insight. Yep, no doubt sloppy loose is normal. And yes, I agree what happens under the upper receiver has very little to do with the accuracy of a chambered round. So yes, I have shot many milspec AR's. So now I will ask you a question. Have you ever held or shot a "accurized" AR? There is no slop or looseness. How long will it stay that way? I have no idea, but it is great while it last.

Regarding accuwedge and "O" rings or shims, I agree, these are bandaids not fixes.


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The real question is... What's your level of expectation accuracy wise out to 1 - 2 - 400 + if that yards? What are you wanting to acheive with your AR, distance, urban build ? You can buy and off the shelf AR, or assemble one from a parts kit, and hit steel @ 1 - 200 yds. even more depending on eye sight and optic.

[ChunkyMonkey]

Thanks for your insight. Yep, no doubt sloppy loose is normal. And yes, I agree what happens under the upper receiver has very little to do with the accuracy of a chambered round. So yes, I have shot many milspec AR's. So now I will ask you a question. Have you ever held or shot a "accurized" AR? There is no slop or looseness. How long will it stay that way? I have no idea, but it is great while it last.

Regarding accuwedge and "O" rings or shims, I agree, these are bandaids not fixes.


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Plenty... but it won't be fair. I happen to be a dealer. I have run into DD mk12 with some play to it.. still shooting moa. Double D demo gun that have seen over 16 k rounds.. sloppy but still moa. Even in hk417 and MWS, we have seen some play between the receivers, and they are still accurate. So 2 things, matching receivers from the same manufacturer do not guarantee anything, and a little looseness as you mentioned may not even be a big deal.

[porterdavid98]

The real question is... What's your level of expectation accuracy wise out to 1 - 2 - 400 + if that yards? What are you wanting to acheive with your AR, distance, urban build ? You can buy and off the shelf AR, or assemble one from a parts kit, and hit steel @ 1 - 200 yds. even more depending on eye sight and optic.

You reduced the discussion to the simple heart of the matter. Almost anyone with any reasonable skills should be able group well and hit targets out to 200 yards. When I started this post I figured somebody would make a statement regarding getting another rifle altogether, like a lock bolt with no slop anywhere. That would have missed my point. I love building (assembling) AR and AK style rifles. However, maybe it is my OCD talking, I have trouble accepting sloppy loose as not fixable. Thanks for your observations.


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[porterdavid98]

Plenty... but it won't be fair. I happen to be a dealer. I have run into DD mk12 with some play to it.. still shooting moa. Double D demo gun that have seen over 16 k rounds.. sloppy but still moa. Even in hk417 and MWS, we have seen some play between the receivers, and they are still accurate. So 2 things, matching receivers from the same manufacturer do not guarantee anything, and a little looseness as you mentioned may not even be a big deal.

Funny (to me) how highly regarded the Daniels Defense brand of high quality AR rifles are. Yes, I have one. Won't sell it or trade it either. But, yep, that rattle sloppiness is present on that gun as well.

As a dealer perhaps you can comment on another observation I had with my personal Daniels Defense weapon. Probably of no real consequence, like my dissatisfaction with rattle looseness, my picatinny rails did not line up perfectly. That is the upper receiver rail did not mate up perfectly with the forward rail of my floating hand guard. For me, I would expect for $1,800.00 perfect alignment from the factory. Have you seen this yourself as a dealer? Fixable? Yes, but it disappointed me big time .


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[Blowby]

Just an observation on the Noveske uppers and lowers. The assembly tolerances are on the tight side. Picked up two uppers on sale at one location and two lowers at another so they are not matches sets. Been shooting these over 8 years and still no slop or wiggle or any movement on either gun with 2,117 rounds on one or them. All my other brands (LMT, LWRC ....) have some movement but it does not affect accuracy or precision when I shoot them.

[Hoser]

Almost anyone with any reasonable skills should be able group well and hit targets out to 200 yards.

Define well and how big of a target...

[USMC88-93]

The tolerance stacking that results in the wobble between the upper and lower (different from rifle to rifle) while annoying for some has little to nothing to do with the accuracy of the rifle if that is part of your concern. Looks like I'm late to the party on this one so never mind.

[porterdavid98]

Define well and how big of a target...

Oh, trying to trap me are you? Actually by most "sniper" standards the AR is not the most accurate of rifles. But, the military thinks hitting 6 inch steel plates at 300 yards is average at best. No bench rest, just sitting, prone, or standing holding a 7 pound gun with iron sights.

My initial post regarding looseness between the upper and lower receiver was not meant to be about marksmanship.


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