How much upper/ lower slop is acceptable?

[mike_the_wino]

Over the weekend I was wrenching on my 6.8 when I noticed some slop. At first it didn't really bother me but as I adjusting things it became more apparent, and more annoying. Since I am setting this up for a hunting rifle I am concerned about accuracy. I checked a few other ARs and they ranged from snug as a bug to mild slop but the 6.8 is the worst of the bunch.

Is this bad? On another note, it's funny how the lowers/ uppers fitment varies so much for all being spec, allegedly.

Off to find those little wedge things in either case.

[NapalmCheese]

Most agree that it doesn't affect accuracy.

If the wedge makes you feel better, use it. Otherwise, an o-ring will do something similar, or you can learn to live with it.

[Junkie]

Spec is a range. They have to make sure the biggest fits with the biggest, so the smallest with the smallest will be a little loose. Seeing as the sights are attached to the upper, I don't see it as likely to effect accuracy.

[mike_the_wino]

Found this on the Fulton Armory site.

Synopsis: Spend the $5.

[russ69]

It makes no difference for accuracy. I had some Colts that would really rattle. The accuwedge will make you feel better and they are plenty cheap.

[Mossy Man]

I just use a small rubber O ring on the front takedown notch.

100% effective, and it can't interfere with you rifles FCG like the wedges can.

[mike_the_wino]

I just use a small rubber O ring on the front takedown notch.

100% effective, and it can't interfere with you rifles FCG like the wedges can.

I'd like to see a pic of that. Can't wrap my head around what you are describing.

[nitroxdiver]

Army TM 9-1005-249-23&P, Page 3-56, shows a upper to lower receiver fit test at the pivot pin and specifies a maximum gap of .020". The test is performed at the pivot itself between the upper and lower. That's the only official test I've ever read about for upper and lower fit, other than do they mate together and does the rifle work
Here's a link to the document. Go to page 3-56 or search .020" to find the picture of how the test is performed, as it'll make more sense if you see the photo.

http://www.cpi-va.us/docs/M16Manual.pdf

[LBDamned]

I just use a small rubber O ring on the front takedown notch.

100% effective, and it can't interfere with you rifles FCG like the wedges can.

^^^this!

use silicone o rings if you can... the rubber ones wear out pretty quick and break... once broken, the upper to lower still remains tight - until you take them apart, then you need to replace...

I've been using silicone for a year or more - it lasts much longer.

I have the accuwege, its worthless... I installed it, realized it's not as good an option as the o ring - removed (now it's in a parts box somewhere)

[LBDamned]

I'd like to see a pic of that. Can't wrap my head around what you are describing.

its a common fix... here are some pics from google search

https://www.google.com/search?q=o+ring+on+front+pivot+lug&client=firefox-a&hs=ty9&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=yjgOVL6mL421ogS-oIGwDA&ved=0CDQQsAQ&biw=1280&bih=667

[IEChuck]

I have a Palmetto upper on an Aero lower and it has slop so I bought a wedge. The rattling is gone, but I can still hide behind my rifle turned sideways and look through the slit to see where the enemy is.

[CK_32]

It makes no difference for accuracy. I had some Colts that would really rattle. The accuwedge will make you feel better and they are plenty cheap.

This^


But to be exact, this is actually incorrect. Tho it's minute to bother arguing over again, Russ is spot on. You will not notice the difference and the accuwedge will fix the "wobble". But technically speaking if a upper were to cant, each election/windage angular adjustment is now changed and is incorrect. So technically speaking for future readers yes it can effect accuracy. For example a optic rifle shooting with adjustments spot on at 400 yards elevation. If canted, POI will not be off.


But again it's splitting hairs and not even worth arguing and I'm sure Russ knows this and was going for he simple explanation to answer the simple question. But I had to put that tid bit on there so no one gets confused reading this then reads about how cant on a precision rig will effect shots. But to OP accuwedge it and call it good. Even if you had tons of wiggle on open irons or 1x optics you won't notice a difference. Even so an accuwedge will fix the issue of canting and "accuracy issues".

[Niviticus]

After use all my lowers and uppers have a little slop in them now. When brand new they fit together tight, but I haven't noticed any loss in accuracy.

[mike_the_wino]

Thanks guys. Those pics LBDamned posted make perfect sense now. And my google-fu failed earlier so thanks for that.

[freonr22]

hey mike, take a peek

http://www.calguns.net/calgunforum/showthread.php?t=315286