MAC Plays with the New SIG MPX Collapsible Arm Brace By SB Tactical

In either a stroke of clairvoyance or lunacy, the ATF arbitrarily decided one in the favor of gun owners with the new approved arm braces by SB Tactical. Of note, the new braces are attached to collapseable rails to create a multi-functional arm “braces” which are legal for any civilian in the United States to attach to a “pistol”. As Tim points out, pistols have advantageous legal characteristics such as not having to apply to cross state lines.

Taking advantage of the ATF’s approval and their inclusion of easily adjustable rails, Sig Sauer is one of the first-to-market with their new arm brace. Modeled directly after their actual SBR/rilfe stock, the arm brace is arguably a bit too small for its “intended purpose.” Like its sibling products, the brace is mounted to the arm of the user via a velcro strap.

Compared to the side folding apparatus, the MP5-style rail “brace system” adds about 2″ to the minimum collapsed length. The rail-style brace/stock system has two positions, with the longest a still short length of pull. Unfortunately, the rails do not deploy on a single press of the locking mechanism. To fully deploy, the button must be pressed twice. For those focusing on speed, the side-folder will deploy faster.

Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

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


  • TheNotoriousIUD

    These things look annoying.
    Too long to shoot comfortably like a pistol, too short to be a rifle.

    • Cal.Bar

      EXACTLY! Waste of time. If you live in a “free state” just SBR it and be done with it. If you live in an “occupied” state like CA, it will soon be considered an “assault weapon” and will be banned anyway – pistol or not. BTW – do I HAVE to shoot it off my face like MAC? Maybe with the operator beard it works better. I try not to backstop ANY of my weapons with my FACE!

      • Richard

        There are certain cities/counties where nfa items are legal in the state, but whoever is supposed to sign off on it simply won’t do it for whatever reason; such as if you do something stupid they think that they will get blamed for it.

        • Cal.Bar

          I know, THAT’s why they have GUN TRUSTS, so you DON”T have to get LEO sign off.

          • sean

            I thought the Gun Trusts where going away?

          • Jeff S

            False. They ease of use is going away. That being said, there is still no CLEO sign off. Trustees and co-trustees will have to submit prints and other paperwork to BATFE. You’ll also have to provide notice to the CLEO that you’re buying an NFA item. He can’t do anything about it though.
            Gun trusts are still valuable tools – especially for estate planning and contingencies like being stationed overseas or in occupied states.

          • milesfortis

            After July 13 (or on that date, depending on who you talk to) trusts and corps will have to submit name, dob, fingerprints photographs etc., etc., etc., of all the people involved.
            There will no longer be a LEO sign off, just a ‘notification’. that a transfer is in progress.

          • AlDeLarge

            To be clear, nobody has to get a CLEO signature after July 13.

          • milesfortis

            Even the LEO sign off is going away next month.

      • Can’t go across state lines with an SBR without ATF paperwork. Now if you are buried deep in the middle of a large state then maybe that’s not an issue, but if you live in a small state or near the border of your state and travel, then it could be an issue.

        Also, as a pistol you can keep it loaded in your car if you have a CPL/CCW, loaded rifle in most states is a no go.

      • Emperius

        The whole point is NOT to submit yourself any personal information to the record database of the government. The whole registration and background check system is the first step towards gun confiscation and complete discrimination in a future way of life, a life of technology, internet-driven society. No American has to bend over and ask permission for what was given in the 2nd. Regardless if anybody can afford a million dollar tax stamp.

        Manufacture, create and transfer all we want, end of story.

  • Vitsaus

    MAC’s gone full ninja.

    • Military Arms Channel

      I can’t find those cool boots though with the big toe that sticks out from the rest that allow you to walk up walls and stuff.

  • Mystick

    In 6 months it will be illegal if put on the shoulder, on a Tuesday, while it’s sunny outside, facing southeast.

    • Cymond

      It’s already illegal if put on a shoulder, regardless of the rest of that.

  • sean

    He likes it all the way out because when the camera isn’t on its against his shoulder…what a joke!

    • milesfortis

      There’s ‘believing’ and then there’s ‘comfirmation’.

  • SLi-Fox

    uhhh sigh…cheek, chest, hip, shoulder…anyone try their forehead or groin?

    • Jack Morris

      They have tried the chin!

      • SLi-Fox

        Ha Ha Ha! I have seen this! It just needs a strap like a special “toy” called an accomadator…

    • iksnilol

      I just wonder why nobody makes a cheek rest. Has been done for crossbows.

      • SLi-Fox

        I believe CAA and some others make a cheek rest.

        • iksnilol

          Just a short tube that you rest your cheek against?

          If so, that should work for the close distances that SMGs are used at.

          • SLi-Fox

            It’s called a saddle. See pic.

          • iksnilol

            I’ve always seen it referred to as a cheek rest. On crossbows it looks like a very short stock.

  • thedonn007

    The sidefolder is more practical. I am not sure why he likes the slider better. You would have better cheek weld with the tube over the sliders as well.

    • Jeffro

      I think he likes it more because it looks like the actual stock, but no need for dumb nfa bullshit

      • Military Arms Channel

        Yup, you nailed it. It looks like it should and I don’t have to pay a $200 tax and put up with endless paperwork BS to take my pistol across state lines.

        • Duray

          I believe it’s just a simple form you can fill out once a year, if you have an idea where you’ll be wanting to travel. Hardly “endless paperwork bs.”

          • Military Arms Channel

            That’s great if you know exactly where you’re going 6 months in advance. I don’t. I travel monthly on short notice, and yes, that’s endless paperwork that would never been approved in time to take a SBR.

          • AirborneSoldier

            A simple form…there should be no forms.

    • K-Gunner

      I have the side folder SBX brace on my MPX. You are correct that it gives a nice cheek weld however, it doesn’t swing open or closed easily. The mechanism can be described as two interlocking wedges that requires a decent amount of pressure to disengage to fold the stock. Admittedly, mine is still pretty new but it’s still a mechanism prone to not disengaging when desired so it is not the speediest to deploy. Also, the SBX adds a significant amount of thickness when folded. It easily doubles the width of the MPX which can make storing in slimmer cases a challenge. I transport mine unfolded for this reason. The slider would be far easier to store in a most compact form.

      Back on the cheek weld, the bars of the slider would not be as comfortable as a tube but it would not be bad either. Anyone who has shot a MP5 with the telescoping stock or an Uzi would say it is manageable. After all, it’s shooting a 9mm.

    • datimes

      I have the SIG collapsible stock on my MPX. My only complaint is that the hair on my face occasionally gets pinched where the stock travels through guides.

  • datimes

    The end of Sept. MAC chose the Scorpio EVO over the MPX. Now the SIG is the go to emergency weapon?

    • K-Gunner

      I think that preference was based, in large part, on the Scorpion’s performance while suppressed being better than the “gassier” suppressed
      MPX .

    • Andrew

      Guess Sig upped his commission check.

      • Military Arms Channel

        Oh the infantile shilling comments never cease it seems. I left the MPX as a pistol and didn’t form 1 it because I’ve known for months about this pending product. I couldn’t talk about it until it was formally released. If this product wasn’t on the horizon I would have form 1’ed my MPX too. As for which is my favorite? The EVO is, but then my EVO is a SBR which isn’t easily transported across state lines. I point this out in the video, but that doesn’t slow the roll of trolls.

    • Military Arms Channel

      You do understand how the NFA works, right? Do you know what’s required to take a SBR out of state, which I travel out of state quite often? The MPX with a brace isn’t a NFA item so it makes sense to put it in a get home bag that I travel with frequently. Suppressors don’t require requesting permission to cross state likes like SBR’s do, so I can toss a can in my bag too. All this is even explained in the video.

  • Cymond

    Of course they approved it. On what basis could they deny the design, as long as it is being used properly? Their previous ruling is clear, it’s perfectly fine as long as you don’t shoulder it. (That’s a pretty huge catch as far as I’m concerned.)

    My paranoid side asks “haven’t you heard of a honey pot?” It’s like they win either way, whether we don’t shoulder the brace out of fear, or do shoulder it and eventually get busted.

    • Budogunner

      This same organization once ruled any shoestring over a certain length to be a machine gun. It took them years to rescind that ruling. I don’t expect logic from them.

      • Cymond

        Yeah, but that ruling was also based on the actual use of the shoe string to make a Garand fire continuously when the string was pulled.

        Add I understand it, it’s now perfectly legal to own a Garand and a piece of string, as long as you never combine them in an inappropriate way.

  • derpmaster

    Lol. You’re allowed to shoot it off of your chest but if you put it in your shoulder pocket you are committing a crime?


    • AirborneSoldier

      This. We need to get rid of nfa, gca, 86, all other gun laws and start holding ppl accountable again. We had a lot less crime when we did that.

      • Duray

        What are you basing that on?

        • AirborneSoldier

          Check crime rates pre 68. The nfa was passed after emotional responses to mob actions that the press hyped over the years leading up to it. 68 GCA, same thing, both Kennedy boys were shot, along with mlk. Emotional responses eventually got the communists, er, antis another piece of what they wanted. A guy used to be able to order guns through the mail, that is freedom, not what we have today, where legislators decide what we can do, or not. Hold ppl accountable for actions, not purchases.

      • At the very least, the SBS, SBR, AOW, and “silencer” rules should go.

        Suppressors are a piece of *safety equipment”, and extensive experience of places where they aren’t regulated show they *aren’t* a criminal issue at all, promote safety, and are more polite.

        SBR, SBS, and AOW categories are in the NFA *solely* as a vestigial and useless way to close a “loophole” that doesn’t even exist. (Originally, the NFA was going to cover *handguns* as well, so wanted to foreclose people shortening long arms to get around the de facto handgun ban. The SBS, SBR, and AOW categories got overlooked when the NRA successfully got handguns removed.)

    • skusmc

      I think absurd is what the BAFTE is aiming for these days.

  • idiocracy

    There is about to be another brace released that does the same thing.