Ask Foghorn: Eliminating AR-15 Wobble


Reader DrewR55 writes:

I have what seems to be a common AR issue. I’ve assembled a Palmetto State Armory AR-15 and the rifle functions perfectly well. But I have what is to me an unacceptable amount of play between the two halves and this bothers me every time I handle the weapon. I am ‘slightly’ OCD and the play annoys me to no end. I understand that this play does not affect the rifle in the least but it bothers so I aim to fix it. Especially because if I spend X hundreds of dollars I want it close to perfect as I can get . . .


In the case of my rifle the two pin holes on the upper are misshapen (too large) and are thus the problem. I’ve considered replacing the upper receiver but two other examples of stripped uppers have had similar issues to one extent or another and I’m tired of this game. I know I can apply an accu-wedge but I’ve heard the cheap plastic wedge can put tension on the halves and cause stress damage. I’ve purchased Armalite NM pins and they seem to solve the problem but I am concerned if they will also stress the two halves and damage the rifle like the wedge is rumored to do? Can you offer some Insight?

You’re absolutely right in that there is no impact on the accuracy of the rifle when there’s a bit of play between the halves of the receiver. The parts that make the gun “accurate” are all housed in the upper receiver, so as long as that’s solid as a rock, you’re good to go. But I understand that the wobble can be annoying and there are ways to fix that.

The wobble comes form the unfortunate fact that while AR-15 rifles have standard specifications and clearly defined dimensions – in theory everything should slide together without an issue –  some manufacturers make their parts slightly smaller or slightly bigger than the specs calls for. This can lead to the two halves wobbling and the shooter being annoyed.


However, just because your gun wobbles doesn’t mean it’s out of spec. The AR-15 was designed to be serviced in the field, so the takedown pins on the front and rear of the receiver should be able to be pushed out using only your fingers. That means the two halves need to have a tiny bit of play, or the friction between the takedown pin and the upper receiver would keep them from sliding freely.

That’s what the “National Match” takedown pins our reader is talking about do. They’re slightly larger in diameter, which increases the friction between the upper and lower receiver and keep eliminates the shimmy. While “solves” the wiggle issue, it creates a new set of problems as there is now an enormous level of friction between the two halves. That puts extra stress on a relatively weak part of the firearm and could cause the pins to snap or the magazine well to crack.

Then again, just about any “solution” to the wobble will do the same thing. Increasing the pressure and friction between the two halves is the only thing that can eliminate the wobble.

The best solution, in my opinion, is the “AccuWedge” widget. Metal “national match” pins  don’t have a lot of elasticity. That’s great for eliminating the wobble, but stresses the parts way more than necessary. The AccuWedge, on the other hand, is plastic. It has some elasticity and will deform under recoil to accommodate the way the gun wants to move. The halves still won’t wiggle, but you’re putting less stress on the relevant parts.

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  1. avatar Halinator says:

    What about piston guns like the Ruger SR556 that can’t use the accuwedge? I’ve been using dental floss around the posts, seems to snug it up… unacceptable?

    1. avatar Pyratemime says:

      Don’t you risk the floss eventually melting? Nylon gunk in the lower receiver seems like a bad idea to me.

    2. avatar J says:

      Old trick but a good one. In the rear part of the lower reciever is the hole were the pin passes through the boss on the upper reciever. I take the gun apart, clean the lower with a degreaser (acetone), and then squirt some clear silicone caulk in that hole. Let is solidify, then reassemble. If there is enough silicone, it will act like an accuwedge. Too litte, add more. Too much, trim the extra away with a razor blade. Works like a charm. Silicone sticks to aluminum a little bit, so it wontt fall out, but you can dig out the plug easily with dental pick.

    3. avatar Dredsen says:

      Wobble absolutley 100% affects accuracy. Ar accuracy is an amalgamation of many components.

      Generally the level of accurization that requires removing the wobble is beyond what users do. Like truing the bolt face and barrel extension surfaces (yes people do that like GAP)

      To say a wobbly lower does not affect accuracy is like saying a wobbly stock on a bolt action is the same. In fact a remimgton 700 , all the parts are seperate from the stock, but yet the stock fit matters big time.

      Granted the things that really open up groups like handguaurd barrel contact (or the more likely gas block handgaurd contact ) are more important but any one buildimg a precision ar needs a solid lockup between recievers.

  2. avatar Ensitue says:

    Sounds like a personal problem, talk to the Padre

    1. avatar G23 to 9 says:

      Bluestone reference?

  3. avatar David says:

    Yeah OCD, me to! That crap really bothers me as well. Palmettoe State Armory has AeroPrecision make there uppers and lowers. I just received 10 Aero lower, and uppers. All are tight at the pivot pin extremely, and a little sloppy at the take down pin. Accuwedges do work, but who wants a snap in piece of plastic put in there 2k build?? Not I Captain! So I matched them up as best I could. Some don’t wobble at all, a few do. But in basic training, all are rifles rattled, crap my stock fell completly off in training!! Let me know what you come up with. Im going to buy more, and even some other brands, just to match up, even though I prefer same namupper andlower…OCD!!

    1. avatar DJ says:

      +1 on issue M4s/M16s rattling. It was rare to be issued one that didn’t.

      1. avatar Sixpack70 says:

        My first M-16 A2 was missing the cleaning kit door on the buttstock and the pins would slide out as I fired. It made an interesting sound through the buttstock as the buffer and spring moved into the stock that was amplified. I still fired 35/40 on my beater rifle. Never had a malfunction either.

      2. avatar dubbs says:

        Own and assembled several AR carbines, and I don’t see a problem as it is only a tiny bit of wiggle.! My agency issues Colt 6940s and they too have a slight wiggle like my BCM upper/LMT lower AR, but just like my personal gun, the Colts still shoot 1 plus MOA.

        I find it weird that many tout the loose tolerance of AK pattern rilfes as a good thing but whine about 1/16″ space in an AR!#!!! ” re-donk’ulous” as they say in the hood…..

    2. avatar Pwrserge says:

      So the beater rifle thing is not unusual going back? That’s a relief. One of the recruits in my platoon managed to break off the stock and buffer tube on the bayonet course. His kill hat was… Impressed.

    3. avatar Mikeinid says:

      I was under the impression that PSA has been making their own lowers for a year or so. I know they used to be Aero Precision. I have seen a couple of the in house PSA lowers, and they are nice and tight.

  4. avatar David says:

    Okay, Mega Arms uses a nylon screw to adjust tension between upper and lower receivers, have a macinest drill and tap your lower and add a replacible nylon set screw, problem solved…about 50 bucks!!

  5. avatar Frank Dio says:

    I have the same thing with my Compass lake, I realized it didn’t affect accuracy at all. I just got over it, mind over matter. Why put stress any where else on the firearm? I figure it was built that way for a purpose. Easy take down most likely. It’s a fine rifle I’m comfortable with the wobble now..

  6. avatar Chase Martin says:

    When prices come down look at tactical innovations lowers they have the slack screw from the factory at a great price, $99 pre panic.

  7. avatar Tim says:

    I use a small o-ring around the front post.

  8. avatar Ensitue says:

    Helpful Hint:
    Nylon washers
    Do not pose black firearms against a white background
    Learn how to use a manual flash

    1. avatar EatIt says:

      Shut up dumbass.

      1. avatar Pat says:

        Wow! What an erudite posting. Your breadth of detailed firearms knowledge is beyond compare.

        It must be inordinately taxing being such an incredible boob.

  9. avatar DJ says:

    I have a New Frontier Armory composite lower, and it fits my Wilson Combat upper so tightly the take down pins have to be pushed out with a tool. It’s got less than 100 rounds through it right now, so I’m hoping when I’m able to buy ammo and shoot again it will loosen up.

    1. avatar Chris Dumm says:

      My New Frontier poly lower is also exceptionally snug with each of the 3 uppers I’ve tried it with. I’m hoping it NEVER loosens up, because I’ve put several hundred rounds through it (before the Panic) and it’s exceptionally accurate as it is.

      My no-name alloy lower uses an Accu-wedge. It’s not absolutely perfect, but its a 90% solution for only about 90 cents and I’ve had no issues with it loosening or stressing the halves.

  10. avatar BrokenForks says:

    One of my acquaintances who was in the military said they used to use a folded cigarette butt in the same place that an accuwedge would go, they are free and plentiful.

  11. avatar TheSleeperHasAwakened says:

    Those wedges work…there are various different kinds and they are very cheap.

  12. avatar Lars says:

    Demon Tactical pin works for my two of three ar’s that have the slight wobble. Not cheap at 40 bucks if you can even find them now but works and looks great.

    Wedges do work but you have to dremel them to get them to fit, easy fix as well.

    1. avatar Gary Parker says:

      Hey bud, That pin you was referring to is it for front and back And where can I find one and what’s the name of it. Thanks Gary Parker…..

  13. avatar Jake F. says:

    I’ve got an AR Frankenstein myself, while accurate and reliable it did wobble pretty bad so I wound up using one of those accuwedge things. The one I use doesn’t feel like plastic though it’s more like a really stiff jelly, you can crush it with your fingers and it springs back. I’ve had it in there for a little over a year now and it seems to work well.

  14. avatar Crunkleross says:

    A JP Tension Pin is the correct fix.

  15. avatar Ed says:

    Or, you could just buy a Colt…

  16. avatar Joseph says:

    Or two………..

  17. avatar JAS says:

    The wobble is MilSpec, by design. If you want your AR lower to not wobble you have to go beyond MilSpec. Some manufacturers do but that opens the possibility of other MilSpec parts not working on your gun.

    The first 1911s were MilSpec, and they were pretty loose. That’s because there was more than one manufacturer and the parts needed to be interchangeable.

  18. avatar ValleyForge77 says:

    +1 on AccuWedge!

    My RRA had a very slight wobble and it drove me a little nuts too. I didn’t what I could do, but then saw an endorsement from the Fulton Armory guy (who knows just a bit about what he’s doing). So I cut down an Accuwedge to fit nicely, but not so tight that I can’t pop out the pin. Oh what a difference. Problem solved for under $5. Now the thing is tighter than a bee’s butt!

  19. avatar Luke says:

    The wobble is intrinsic to the AR platform.
    Take advantage of the panic buying going on.
    Sell it for more than you paid for it.
    Use the money to buy a gun that doesn’t wobble.
    Pocket the difference.
    Everyone’s happy.
    (Except AR fetishists.)

  20. avatar Tony says:

    Use 1/4th of a foam earplug works great under the Rear Lug. Place in in the rear where the Back lug of the upper will smash it down, Should have enough tension where you need to push down on the Upper for the Pin to fit through, creating tension on the upper against the Pin. Its a home made accuwedge for “high-shelf” Lower receivers where an “accuwedge” is too thick for.

    For “Low-Shelf Receivers” you may want to use an entire ear plug.

  21. avatar Matt says:

    I eliminated the wiggle problem with an AR15AccuShim.

    1. avatar Matt says:

      The loose problem is caused by manufacturers trying to adjust their receivers to fit the other guy’s receivers. That’s why the takedown pin lug on many forged upper receivers has a fits-all-slot instead of a perfectly round hole. Slots measure around .250″ x .265″ and rarely will a .248″ mil spec pin contact the front or back of the slot. Only the top center or bottom center of the pin contacts the slot. All of the ingredients for wiggle come straight from the factories and are enhanced in the first 200 rounds.
      Some upper receiver pivot pin lugs are wider than others and lugs that do not fit the lower well should have shim washers placed on each side.
      To correct loose pins I use oversize .251″ Armalite NM Pins which will cost about as much to ship as the pins cost, phoning Armalite generally gets a lower ship rate. If your receiver bores are lightly over .250″ the Armalite pins should drop in however gauge your receiver bores first.
      There is only one thing an AccuWedge is good for and that is it works as a buffer. With an AccuWedge receivers will still twist side to side according to pin fitment.
      My other fix as mentioned in an earlier post is an AR15AccuShim. Unlike other remedies the shim installs in the upper receiver and removes 100% of the wiggle. It takes about 30 minutes to fit the shim so you’ll need working experience with the AR15 platform.
      In a nutshell matched receivers are the only way to go if you want a truly precision built rifle but if you’re in the same boat with loose receivers like a lot of people are, there are remedies available.

  22. avatar Johnny5 says:

    This all seems a bit ignorant to say there are less stresses without proper fitting. Sure there is more steady subtle tension on the receivers with a “fix”, but there’s also a steady pressure between the barrel extension and upper receiver and you don’t see people complaining those are fitting too snuggly. When the fit is loose, the parts slam around; when the fit is tight, they smoothly transfer energy. Think about it. Would you rather push another car with your front bumper with them touching to start, or with a 5 foot gap in between while you speed up? The answer seems obvious.

  23. avatar Matt says:

    Wobble works with full auto intended to be serviced in the field. But for a precision built semi auto intended to be serviced in a shop or home and produce tight groups wobble is no more acceptable than a loose scope. And with all due respect Mr. Foghorn you may want to rethink the possibility of snug fitting aluminum receivers snapping a steel takedown or pivot pin or that friction between the halves may cause sparks to fly or other calamities to occur.
    A sponge-bob AccuWedge is by no means a destructive device and works only as a buffer. It pushes up against the takedown pin lug and that spreads the receivers apart and the wobble continues but in a slower motion. Yes the AccuWedge is guilty while once again receiver slop slips through the backdoor…Who concocts this stuff?
    All that has to be done to stop wobble or side to side movement is to reduce the clearance between the halves to zero. You can bring the receivers together or you can shim to zero. To cause a stress crack you would need to squeeze the receivers together in a vice and hammer the pins in. A pin that can be pushed by hand and fits snug will not cause a stress crack…not happening.
    What are destructive to receivers are loose components that get a running start and slam against each other as one other writer already has indicated.
    A good pair of matched receivers may not allow light to pass through the seams and people pay big bucks for those in order to avoid the gremlins associated with mismatched receivers. For the rest of us with mismatched receivers who do not fall for the list of excuses made to justify loose there are fixes that do stop the receivers from wobbling. Another is an AR15FlatJack. Just by looking at one you would doubt it works but indeed it does work, better than advertised. Just thought I would update the topic.

  24. avatar Daniel L Varner says:

    On my 6.5 Grendel about a half inch square cut from my target took out the slop and the pins go in easily

  25. avatar Scott says:

    I have a pivot pin that seems like it is loose in the hole. Thinking about getting a .248 pin, figured if it fit by hand it wouldn’t cause problems.

    Also power custom lower receiver shims do a good job of removing side to side play

  26. avatar Jim Stephens says:

    The National Match Shim is the fix, It’s the real deal. Rock solid when installed. Takes a little fitting, but well worth it.

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