Install a Buffer Tube With the Right Tools – TFB Modification Minute

You know that awesome stock you have been eyeing? That one that only comes in Mil-Spec diameter, but your rifle has a commercial diameter buffer tube? This week’s Modification Minute tackles that very problem by replacing the factory commercial buffer tube with a high-quality Brownells Mil-Spec buffer tube. Enjoy!

Please support our sponsor Brownells. Products in this video:

Brownells Mil-Spec Buffer Tube – $25.99

Magpul Armorer’s Wrench – $75.95

Bravo Company QD End Plate – $16.99

Geissele Reaction Block – $99.00

Starrett 5/32″ Center Punch – $8.99

Brownells Oxpho-Blue – $9.99


Patrick R

Patrick is a Senior Writer for The Firearm Blog and TFBTV Host. He likes guns and has liked shooting guns for as long as he can remember. You can follow Patrick on Instagram @tfbpatrick, Facebook, or contact him by email at

The above post is my opinion and does not reflect the views of any company or organization.


  • GunSnobMTilligitimi

    The “buffer” is the weighted piston at the front end of your action spring. The “receiver extension tube” is the technically correct name of the part you’re talking about. “Buffer Tube,” though not technically correct, I feel is more acceptable than just calling it the “buffer.” Granted, I’m sure you only have so many characters to fit into your title. It would be a bit long were you to use the proper terminology.

    [EDIT]: Just saw in the URL: “vague-title-buffer-tubes”

  • Tim

    My Lord. “How to spend more munny on crap you don’t need”, chapter 437.

    Meanwhile, you can buy a brand new S&W M&P AR-15 Sport II for < $500 w/free shipping.

    • Tim

      ….but I’m NOT bagging on Patrick! Love the guy & he does great work! I’m just broke!

    • Robert Fory

      PSA had it today for $399.99

  • st381183

    Torque wrenches should be attached perpendicular to any extension like barrel wrenches, castle nut wrenches, etc for accurate readings of the torque being applied.

    • Steve

      First thing I thought of when I saw the article title and thumbnail…

      Nice job telling people how to do it right, then applying a huge amount of torque over spec. because you don’t know the basics of using your tools.

    • Steve

      And technically – you don’t want the extension perpendicular. When it’s a crow’s foot, the difference is negligible. When it’s a long extension it should lie within the arc of the circle formed by the torque wrench handle (center) and the ratchet head (diameter).

  • JSmath

    Gdamnit Patrick, why are you teaching people the wrong way to use a torque wrench. Especially as the thumbnail image. If you resolved the setting for the lever arm increase and adjusted accordingly, you should have, at the very least, annotated it in the video.

    Just eyeballing it, if that torque wrench was set to 40ft-lbs, the nut had around 70ft-lbs applied to it.

    • Steve

      At least 70…

    • Patrick R. – Senior Writer

      The video length does not allow for detailed explanations. A calculator was used to determine the correct setting.

      • JSmath

        You’re supposed to be a jolly firearm leprechaun, Patrick, not a firearm troll. We trusted you. 🙁

        • Patrick R. – Senior Writer

          Never trust an Irishman 😉

          • CavScout

            “The Irish were rotten Indian fighters…”

            Also, this is the Midway USA style video of installing a receiver extention. $$$$$ on the tooling.

          • Patrick R. – Senior Writer

            You mean Brownells?

    • Klaus Von Schmitto

      Uh-Oh. I guess my barrel nuts aren’t going to come unscrewed.

    • neckbone

      Please put up a proper video yourself.

  • valorius

    You forgot to list the most important tool of all, which is the torque wrench. A high quality torque wrench can cost several times the cost of an AR-15.

    • Mystick

      Of course, that all means nothing if you use it wrong – such as demonstrated here.

      • Charlie Victor Alpha

        First thing I noticed too, “How to install a buffer tube, correctly”. Ahh, nope.

  • The Dude (Noveske Fan)

    First off you should never use tools to install a action tube, second it should be hand tight and clogged with steaks.

    • Holdfast_II

      T-bone or sirloin?

      • The Dude (Noveske Fan)


        • 22winmag

          The wooden variety of stake, commonly driven through the hearts of vampires.

  • Scott Tuttle

    one more bitch while we’re all at it, using facebook to host videos isnt probably a good long term solution. they’re pretty anti gun.

    • Haulin’ Oats

      It’s most likely a part of the brownells sponsorship and marketing to use facebook.

  • Ark

    You don’t need all that. A basic bench vise and any generic armorer’s wrench will do the job. You really don’t even need a torque wrench, though if you have one it’s a good idea to use it. All you need to do is get the castle nut reasonably tight and stake it in place. I did my first one with a flathead screwdriver and a few taps from a hammer. The castle nut torque doesn’t affect accuracy, it’s literally just there to hold the buffer tube on.

    • Patrick R. – Senior Writer

      If I have the tools, why not use them?

  • USMC03Vet

    That is pretty expensive to change a stock. I could have sworn the internet said AR15 like Lego! I changed my AK stock and only needed a screwdriver.

    • JSmath

      In most the cities and towns I’ve lived in, you can walk down to an autozone/oreillys/etc to rent all the tools used, except the castle nut wrench.

      The cheaper solution would have been to check your extension before buying a replacement stock, then the video would have been completely unnecessary. Gotta sell parts!

  • 22winmag

    Is it true staking was specified before Loctite came on the market?

    • DIR911911 .

      Loctite was invented in the 50’s and available in the early 60’s

  • Ian McCollum

    I hear that positioning a torque wrench wrong will cause it to explode and kill you!

    • Spencerhut

      The .gov spent a lot of money teaching me how to use tools like torque wrenches properly. If you are not going to use a torque wrench properly, just don’t bother with it at all. All you are doing is giving yourself a false sense of doing a proper job.

      • Qoquaq En Transic

        Ok, so I’ll ask since I’ve never been taught at all.

        When tightening up a barrel nut on an AR upper, you have various length tools (extensions) for that in which one places the torque wrench.

        Is the torque wrench (set to the appropriate torque spec for the nut) supposed to be at a 90 degree angle to the extension?

        In other words…

        Looking down the barrel from the muzzle end, the barrel nut tool (extension) is pointing at the 3 o’clock position and the torque wrench is pointing at the 12 o’clock position? Is this correct?

        Thanks for your input.

    • JSmath

      Ya, you tell those retards who’s boss. Torque specs are for big dumb losers.

  • M-daher

    you shouldnt need anything more than a hammer, a brass punch, and a center punch to install a buffer tube.

  • Walter E. Kurtz

    Will the next mod involve repairing the upside down ambi selector? The horror…the horror..

  • Mystick

    Torque wrenching: You are doing it wrong. Using that technique(and extension tool), it’s very easy to over-torque due to the extreme leverage – and we’re talking about aluminum here(probably – possibly even plastic for those oddball lowers)… not really forgiving when it comes to torque stress on threads.

    That wrench isn’t going to be accurate under those conditions. You should be using a collet style torque wrench with the proper collet key for the nut)You might have to make a specialized key – but you are doing a specialized thing)

    If you ARE going to do it with that socket torque wrench use a crowsfoot socket wrench, where the mechanical leverage at the point of measurement is minimized.

    The proper tools get you close to proper work.

    • Patrick R. – Senior Writer

      Used a calculator to find the correct setting on my very out of spec wrench. These videos aren’t really a how to, they are supposed to show people that it isn’t that hard to change something and give them a starting point. 60 seconds isn’t enough time for proper instruction.

      • Mystick

        I see…. many people would use them as such with “instructive” titles such as the one for the video, though. Might want to disclaimer that(I know, I know… our world today sucks ;/)

  • RICH

    Not that this is rocket science but for an individual that is doing this install for the first time it would have been a lot more applicable if it ran at a speed where the viewers could read it ! !
    I also use blue Loc-Tite on the castle nut on my buffer tube installs.

  • Audie Bakerson

    Question: What the hell IS commercial spec? I can find the difference, how to tell the two apart ect. but nothing about what led to this abomination existing or continuing to exist.

    • Marcus D.

      You usually find out the hard way, since few vendors tell you what their spec is for either the lower or the tube. I found out the hard way, having bought a commercial spec lower and a mil spec tube that won’t thread correctly. I am GUESSING it is the pitch of the threads, and/or the diameter of the tube/hole.

      • Patrick R. – Senior Writer

        No. The threads are the same pitch and size. The tube that fits into the stock is larger on the commercial tube. There are more differences, but that is all I am willing to type out on my phone.

      • Audie Bakerson

        I know how to tell the difference, but I asked why anyone would make such a thing.

    • st381183

      Commercial spec has a slightly larger outside diameter than a milspec tube and an angled end cap. The commercial spec is made from cheaper aluminum and has thicker walls than the milspec so the commercial spec is thicker requiring a larger butt stock. Commercial buttstocks will fit milspec tubes loosely while milspec buttstocks are too narrow for commercial tubes. The tubes both work fine but commercial spec is usually used on cheaper budget conscious rifles.

      • Audie Bakerson

        It costing less vaguely explains how it came to be, but not who did it.

        • st381183

          It was DPMS or Bushmaster back during the Clinton Assault Weapon Ban. It was a way to cut corners and meet demand.

          • Audie Bakerson


  • Qoquaq En Transic


    It would appear that the lengths are the main point. Seems it doesn’t matter whether the wrench is in an in-line configuration OR a 90 degree configuration with respect to the extension. Just don’t do it an any other angle?

    • Doctor Jelly

      You can calculate any angle you want (including having the wrench extend towards your hand instead of away from it), but it’s very uncommon to do so as most don’t care to commit the formula to memory. I have to use torque wrenches on virtually every fastener I touch due to the nature of my job, and because the manuals give you only a single torque spec, it’s easier to do everything with sockets (no calc required) and with the torque adapter at 90° to the torque wrench (no calc required).
      If you cannot reach the fastener with the torque wrench at 90°, then you should calculate the torque based on how much extension you add as you have effectively created a longer lever (which is a force multiplier). A common tool in the mechanic world is a torque adapter or “dogbone”. The standard size is 2″ from the center of the torque wrench square drive to the center of the fastener to make the calculation easier.

      Ultimately, nothing broke so I say no harm no foul, but for people who don’t understand it makes a difference (and people who are watching basic videos like this tend to be new and uneducated in mechanical assembly techniques), the video really should be amended to point out the calculation necessary or show the more common 90° method. A quick Google search gave me this calculator that takes into account any angle you want. So if we pretend Patrick’s setup was straight (looks like it was a few degrees off, but not enough to matter on something like this), the torque adapter (buttstock wrench) at 7″ long (center of square drive to center of fastener), and the torque wrench at 14″ long (center of square drive to center of where your hand applies the pressure), then he should have the wrench set to 26.7ft-lbs to achieve 40ft-lbs at the nut.
      To avoid the url filter, I just searched ‘torque adapter calculator’ and the first result was at cncexpo that allowed the angle to be taken into account.

      • Qoquaq En Transic

        Many thanks, DJ!

  • Joshua Graham

    There is a certain pride in doing a thing yourself, but in this case it would make more sense money-wise to just pay a gunsmith 10 bucks to do it. I my local one replace the commercial tube on my RRA AR15 with a milspec one I provided for 10 bucks and he did it and staked it in place while I waited.

  • David G

    Sorry, I already sold all of my guns per your advice Patrick. No mil-spec or commercial buffer tubes to swap here.

  • GI

    Maybe because he didn’t bother showing it?

  • JJ

    No criticism on staking the end plate/castle nut, as it makes sense on a hard use item. I just wonder how many folks building their own do that. I have on a few over time but for the most part just tighten it and forget it. In almost 3 decades of working on these, I’ve never had a castle nut come loose either. I’ve seen with or without staking from company built ones. Who stakes, who doesn’t and why?