Ask Foghorn: Eliminating AR-15 Wobble

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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.

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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.

[Email your firearms-related questions to “Ask Foghorn” via guntruth@me.com. Click here to browse previous posts]

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About Nick Leghorn

Nick Leghorn is a gun nerd living and working in San Antonio, Texas. In his free time, he's a competition shooter (USPSA, 3-gun and NRA High Power), aspiring pilot, and enjoys mixing statistics and science with firearms. Now on sale: Getting Started with Firearms by yours truly!

31 Responses to Ask Foghorn: Eliminating AR-15 Wobble

  1. avatarHalinator 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?

    • avatarPyratemime says:

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

    • avatarJ 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.

  2. avatarEnsitue says:

    Sounds like a personal problem, talk to the Padre

  3. avatarDavid 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!!

    • avatarDJ says:

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

      • avatarSixpack70 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.

    • avatarPwrserge 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.

    • avatarMikeinid 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. avatarDavid 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. avatarFrank 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. avatarChase 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. avatarTim says:

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

  8. avatarEnsitue says:

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

  9. avatarDJ 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.

    • avatarChris 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. avatarBrokenForks 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. avatarTheSleeperHasAwakened says:

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

  12. avatarLars 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.

  13. avatarJake 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. avatarCrunkleross says:

    A JP Tension Pin is the correct fix.

  15. avatarEd says:

    Or, you could just buy a Colt…

  16. avatarJoseph says:

    Or two………..

  17. avatarJAS 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. avatarValleyForge77 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. avatarLuke 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. avatarTony 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. avatarMatt says:

    I eliminated the wiggle problem with an AR15AccuShim.

    • avatarMatt 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. avatarJohnny5 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.

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