Sig AR-Pistol Arm Brace – KAK Super Sig Buffer Tube, the Perfect Fit for Improvised SBRs

KAK Sig Tube 10By David Higginbotham
KAK Industry, LLC
AR pistols have always seemed a bit odd to me. They’re almost too heavy to be fired as pistols. The odd tube sticking out of the back makes them look unbalanced. Recoil is so jarring that repeat shots are slow. You can fire them as you would a pistol, but why would you? You can get all jammed up on the gun and shoulder the buffer tube, but why? I tried them out. I wanted to believe, but I didn’t get it. Then came Sig Sauer’s Pistol Arm Brace. The brace makes a great improvisational stock, but you really need the right buffer tube between the pistol and the brace to make the most of it. KAK’s Super Sig SB-15 Pistol Buffer Tube insures that the brace-as-improvised-stock (or even as an arm brace) performs exactly as it should, every time.

The brace itself isn’t compact, but it is effective. The strap keeps both sides together.

The brace itself isn’t compact, but it is effective. The strap keeps both sides together.

Sig has just sent us a SIG556 pistol to review. It is a great gun. As a pistol, though, it is almost impossible to shoot accurately. It seems a bit odd to talk about the SIG556 without an arm brace, so we got back in touch with Sig and they sent one for the review. But they didn’t send a buffer tube. As it is almost impossible to attach an arm brace to a SIG556 without a buffer tube (or a lot of duct tape), I went in search of the perfect match. Enter KAK Industry and the Super Sig SB-15 Pistol Buffer Tube.

Before Sig launched its arm braces, its line of rifle-caliber pistols was a popular starting point for those wanting to register short-barreled rifles (SBRs). With a stock attached, the Sig pistols become formidable SBRs. The arm brace began its life as an arm brace, something you attach to a buffer tube that allows you to strap the pistol to your forearm. Yet recent rulings by the ATF indicate that it isn’t illegal to shoulder an arm brace. And now these pistols and braces are flying off the shelves. KAK’s new dedicated tube is perfect for those who want to skip the SBR registration process and get serious about using arm braces on AR pistols.

The KAK’s Super Sig SB-15 Pistol Buffer Tube, two sleeves for adjusting the length of pull, a buffer and spring and a QD endplate.

The KAK’s Super Sig SB-15 Pistol Buffer Tube, two sleeves for adjusting the length of pull, a buffer and spring and a QD endplate.

At first glance, the KAK tube looks like many other buffer tubes. It is round, aluminum and has that flat black finish that defines the AR platform. Yet there are a couple of subtle differences that make the new version stand out. The first is the necked step on the outside of the tube. The arm brace’s tube sleeve is 6.5 inches deep. The KAK tube is necked at that length, which keeps the arm brace from sliding toward the gun as the recoil pushes the tube back in the brace. This makes for an ideal SBR stock. Length of pull isn’t as much of a consideration when you’re trying to keep the whole package compact. Even oversized oafs like me can jam up on a short stock when we have to.

The rear of the Sig arm brace is wide enough to make an effective stock. After shooting more than 500 rounds through the SIG556 for the initial portion of the gun review, I can’t feel any before/after difference in my shoulder. And this brace never moved. It was easy to muscle on and off, yet stayed true during shooting. There was no forward movement and no rotation.

The sleeves add almost two extra inches and allow for more cushioning from the brace.

The sleeves add almost two extra inches and allow for more cushioning from the brace.

And if you do want some extra length of pull, KAK makes two collars that can be used alone, or together, to add anywhere from .625 to 1.25 to 1.9 inches of extra length. The real appeal of the collars is the extra length, but there is an added benefit: extra give. With the brace and tube mated completely, the end of the tube is flush with the end of the brace. If you do happen to shoulder it oddly (like against your collarbone instead of lower on your chest), that aluminum is going to bite. With the spacers on the tube, there is an equal length of rubber displaced at the end. With both spacers on, there is almost two inches of rubber at the end. While it isn’t even as squishy as some shotgun stocks, it isn’t aluminum. The squishiness combined with the KAK tube’s ability to keep the arm brace from moving makes the perfect combination.

As a control in these experiments, we put the brace on a typical AR pistol buffer tube. The difference was noticeable from the moment of instillation. The brace was much harder to get on the tube. As it is rubber, the brace didn’t tear out, but the fit was tight. And when shooting, the brace crept down the tube, as there were no stop to keep it still.

This is the second generation of the KAK arm brace tube. This one attaches with a typical endplate and castle nut. The endplate they sent us has a QD sling mount, which is the perfect position for a QD sling on an SBR. The endplate also has a tab that mates with the tube to keep it from turning, so there’s no real need for Loctite. If your AR needs the buffer and spring, those are included in the kit. The whole package includes the tube, the buffer and spring, the castle nut and the QD endplate for $93. The extension sleeves are an additional $12. KAK even sells the Sig braces, too. From my perspective, it is an easy choice. Check out KAK.

{ 32 comments… add one }
  • B.Bishop February 5, 2017, 10:23 pm

    Sure is enlightening to see all the supposed “patriots” who are terrified of Jackboots with no Constitutional authority whatsoever…speaks volumes for the current state of affairs in this country, that people want to cower in the corner instead of facing the boogeyman with a middle-finger held high and proud…

    The ATFE has Z E R O authority to write or interpret the law; Moreover, an ‘opinion letter’ is nothing…it has no legal precident and no authority in a courtroom…it is a useless scare tactic aimed at paranoid fools and worse yet, it works…flawlessly

    Look at the paranoia surrounding 922r…its a garbage ruling that is absolutely unenforceable, yet, irrational paranoia feeds the stupidity to the point people stop thinking and fall in line behind ignorance…same thing with everyone’s fears about “constructive intent”…its all laughable

    The posters who somehow think worshipping at the feet of the ATFE,begging for their permission to exercise your Constitutionally protected Rights, are the problem…feeding their naricissism and granting them authority over regulation and interpretation of law; They are not the Supreme Court nor Congress, therefore they are a rogue faction of Tyrannical Insanity and nothing more…

    They can go fornicate themselves…MOLAN LABE

  • Linda Dee August 19, 2016, 10:41 am

    I am a disabled veteran with 1-Arm The KAK to me works better on my ar-15 handgun than the sig And comes with a Atf paperwork for use If the government which we all know is going crazy says-I can not use this & I who have fought for them. I’m disgusted with what’s going on KAK industries ROCK with their arm brace. The government can kiss my white America you know what. Peace out brothers

  • Ringo Lapua August 1, 2016, 11:48 am

    As I read about this debate whether a Sig brace is or is not and SBR, I sit back and try to rethink the WHOLE CONCEPT OF THE BATF, who are they, who gives them the power that they wield and more important is the knowledge of WHO CAN CHANGE OR TAKE AWAY THEIR POWER.
    Now that this line is drawn in the sand, please understand that it is CONGRESS who can change or abolish the BATF. Republicans control both houses of Congress, so why has this not been an issue? The President administers the BATF and like the IRS and DEA, the BATF can be and is used as the Presidents GESTAPO.
    Currently, the Democrats and Hillary Clinton are screaming GUN CONTROL and the banning of Military Style Weapons (whatever that means or is determined). We all know that the military does not use AR or AK semi-automatic weapons other than handguns and bolt action sniper rifles. So WHY does Congress allow (at a high cost to the taxpayers) allow the BATF to lord over the semi-auto domestic non military weaponry. Some say because is a source of revenue, but I say that the BATF was never organized for that purpose and should be reset to its original function and that is to keep MILITARY GRADE weapons out of the hands of the general public (machine guns, hand grenades, bazookas, shoulder fired missiles, C4, naplam etc.). The word STYLE is a fantasy of the Democrats because STYLE does not kill masses of people faster, fully automatic weapons do and they are not offered to the general public buying over the counter.
    We need to write to the NRA and all of our Congressman and ask them to restrict and revise the BATF to preside only over Military used and approved weaponry. Non-military weapons, sig braces, suppressors and short barreled semi-auto rifles would NO LONGER be under their jurisdiction. AM I CRAZY OR AM I MAKING COMMON SENSE?

  • Allan January 18, 2015, 10:17 am

    Well,it is 1/18/15 and two days ago, the ATF rescinded their legal ruling on shouldering the SIG Brace. It is an NFA violation now. Do not shoulder a SigBrace! File a form 1 and you now have a rubber stock SBR and are legal…

  • Bryan May 29, 2014, 7:19 pm

    You know all the controversy from the ATF for the very thing that you post pictures of… Are you playing with a full deck? It’s an arm brace and that is all. Seriously who’s side are you on and why add fuel to the fire?

  • David Nelson May 29, 2014, 8:26 am

    The arm brace is also available for AK pistols and comes with a letter from ATF stating that it is not a rifle stock and therefore does not require SBR paperwork. Have fired SIG and AK with stabilizing brace they are absolutely awesome.

  • joe May 28, 2014, 3:53 pm

    Agreed! If it’s under 16″ and it has a stock (which in the photo above is exactly how it’s being utilized) it is most definitely an SBR.

    • Chuck Backus May 28, 2014, 6:18 pm

      joe……it “IS NOT” an SBR! It is a pistol with an arm brace as defined by Batfe. Nothing more, nothing less. We must not shoot ourselves in the foot (no pun intended) by defining / describing it as anything else.

      • Joe May 29, 2014, 2:04 am

        First I really like the setup, and Sig knows how to make quality firearms, but Look.. you can call the “armbrace” whatever you want, and i’m well aware of what constitutes an NFA regulated short barreled rifle. Unless the barrel of the PISTOL is at least 16″ in length and the overall length of the firearm with the attached stock (which is essentially what this armbrace functions as) totals at least 26″ overall… you pretty much have an SBR. Look at the picture at the top of this blog, the gentleman in the photo is utilizing the brace as a stock, so that right there proves it can be operated as a stock, and you cannot legally install a stock on a pistol without an SOT. Sorry

        • Chuck Backus May 29, 2014, 11:11 am

          joe……I call it what Batfe calls it, period. For you to play “smart guy” and call it something IT IS NOT is foolish at best and stupid and destructive at worse. Batfe has already ruled that the Sig brace DOES NOT make an AR pistol into a SBR, so your statement is bunk……however, as stated above, with all the anti-gunners who would love to fire-truck us as often as possible we must call it what it is, not what it “looks like”. I have a DB15P with a sig brace, 7.5in barrel, and I use it as it was intended, but I will not say I use it any other way………Lets use the common sense that god gave us, and not do any harm to ourselves when it comes to us 2nd Amendment protectors FINALLY getting a break from the kooks that make the rules. We know how it can be used, but DO NOT need to gloat about it openly. Wise up bucko………

          • Dan July 18, 2016, 10:14 pm

            Chuck- at first the ATF gave the green light on the Sig Brace, however after all the social media photos of people shouldering it, they revise their statement . They been released a second statement saying that if one chooses to shoulder the brace they have altered the original design of the brace and therefore qualifies it under an SBR . In other words they want your money and want you to file a form 4 and paid $200 tax stamp to make it official

  • Bisley May 27, 2014, 6:38 pm

    The appropriate cure for the problem is repeal of the NFA, at least as far as short-barreled rifles and shotguns and silencers. If full-autos are to be regulated at all, it should be in a cheaper, simpler, more practical way. There needs to be a movement to get rid of this stupid, impractical law (after the Obama clan is removed from power), rather than look for ways to, sort of, get around it.

  • Lee Kramer May 27, 2014, 4:38 pm

    I have been perusing the comments and I’m going to say some things now that will be roundly loathed by most of the comments on the terminology used in this article. Remarks about “giving the ATF ideas”, is a crock. They have had and will always have these ideas, whether we talk about them or not. Today most people who vote are simple pantywaists, but they are the ones sealing the destruction of our Former Republic and our Liberty. I’m 59 now and have watched as large quantities of our Liberty have given way to the present level of tyranny we live under. I still remember a great deal of Liberty and it’s freedoms which no longer exists today. It was taken for granted then and it still is now. Most of the LAW now concerning firearms was nonexistent when I was a kid. The 800 pound gorilla in the room that nobody talks about is what the founders of the republic stated often was necessary for Liberty to exist and continue. That is an ugly and frightening reality which it seems many here won’t consider but is nonetheless true. A time of watering the tree of Liberty is coming. When I read these comments about you shouldn’t say this or say that makes my blood boil. There is also still a 1st Amendment too. If the reader can’t figure out what this means then the beast has won and we all may as well disavow our GOD given and not ATF given RIGHTS and just surrender right now folks. The man writing article has every right in the world to use whatever terms he damn well pleases. But, I fear the naysayers will be the first to run and hide when you know what hits the fan. Lets not kid ourselves that day approaches swiftly. The time is coming soon to man up for Liberty or surrender to this incremental tyranny I have watched progress like a cancer through the years. Voicing thoughts that you fear others will hear and then THEY make a RULE in the guise of LAW tells me we are closer to that day then I first thought. You see folks man make RULES and then calls it law, but the fact remains that GOD is the true giver of LAW and the Liberty with is. Liberty doesn’t come from all of the tyrannical alphabet soup agency’s that have come to impose upon us today. When we accept these rules, and once we understand the consequences and won’t rise up against it then we are no better then the elites making these rules they call LAW. Anyone who doesn’t get that, just tells me we are doomed already. Read some of the thought of one of our founders:
    “The issue today is the same as it has been throughout all history, whether man shall be allowed to govern himself or be ruled by a small elite.”
    –President, Thomas Jefferson
    “The natural progress of things is for liberty to yield and government to gain.”
    –President, Thomas Jefferson
    “If a nation expects to be ignorant and free, in a state of civilization, it expects what never was and never will be.”
    –President, Thomas Jefferson
    “The strongest reason for the people to retain the right to bear arms is, as a last resort, to protect themselves against tyranny in government.”
    –President, Thomas Jefferson
    “The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants. It is its natural manure.”
    –President, Thomas Jefferson

    • Chuck Backus May 27, 2014, 11:49 pm

      Lee…..Most, if not all, of us on here today, I assume, do not disagree with your post, however, I (I speak only for my self) disagree with your methodology. Yes, you are correct that we must fight to retain our GOD given rights as they were written in our Bill of Rights by our founding fathers. Having said that, we are in a time of political correctness and must be aware of those who are around us in physical as well as listening form. It has been proven beyond a reasonable doubt that there are individuals, groups and cultures who wish to do this country harm by any means possible. It is by the 2nd Amendment that their transition process has hit a wall as it was steam rolling forward. I, myself feel that our words within the confines of our own homes, with like minded families and friends, are safeguarded, but not on the internet and forums such as these. (to be fore-warned is to be fore-armed). So do not judge those who seek to keep certain subject matters quiet to mean that they are afraid to speak out. As you say, there will be a time in the not too distant future where we will all have to speak with our actions, and, words will then become meaningless. You and I are of the same age group, and I relate to what you remember as “what was”. I have spent 20 years as an 11 series soldier in the Army, I have lived and gained friendships all over this country of ours, and, I have lived and gained friendships all over this globe of ours too. My point is…there are many people, both sexes, from many walks of life, with varying degrees of knowledge and education, from a multitude of locations both domestic and foreign who think just like you and I do. But do not pre-judge them because their methods of achieving “the same end result” are different from yours. Think about it my friend………..

  • DR May 27, 2014, 1:16 pm

    Really?!! Improvised SBRs?! Take this article down. You took and foot and now you want a mile! The ATF is going to take this away because people are abusing the intent of their decision. It’s a pistol stabilizer! It’s not an improvised SBR. What an amazingly irresponsible article. Take it down!

  • JT May 27, 2014, 11:43 am

    For the price of the brace and tube, you could get a tax stamp and regular stock and buffer tube. Also, with a stamp, when ATF reverses their decision, you’ll still have a usable firearm. Look at the ATF definition of rifle vs pistol; one has a buttstock and the other doesn’t. Therefore, like it’s been for years, shoulder firing makes it an SBR. This Sig Brace allowance is bound to be reversed soon.

  • jim lewis May 27, 2014, 11:28 am

    great write up, have had this setup for a couple months now with great sucess. prior to this i had a ert sling, and opmod eotech on. this the sling pulled tight you could get a good cheek weldment againest it. hit man size targets at 100 yards. ceap option to the brace.

  • jim lewis May 27, 2014, 11:27 am

    great write up, have had this setup for a couple months now with great sucess. prior to this i had a ert sling, and opmod eotech on. this the sling pulled tight you could get a good cheek weldment againest it. hit man size targets at 100 yards. ceap option to the brace.

  • ARluv May 27, 2014, 10:44 am

    People were shouldering the AR15 pistol since its appearance on the market. It didn’t make it an SBR before and the stabilizing brace doesn’t make it an SBR now. I was at a wounded warrior event this weekend at a local range. You should have seen how many vets were out there shooting the stabilizing brace the way it was designed. They were also shooting at from the shoulder. Sildefire has been out for 5 years now and it makes a semi auto gun shoot full auto. The ATF is bound by certain definitions, in order for them to change things they’d have to seriously revamp they entire NFA and GCA.

    • SteveFAL May 29, 2014, 12:33 am

      BATFE is a rouge agency that does pretty much whatever it wants. It enacts laws without congressional aproval, in the free & clear. Why antagonize them? Even if they are OK with their definitions of these items for now, once the Brady/Schumer/Bloombergers get wind of it, they will ride the BATFE like a $2 ‘ho until all such accessories are banned. If BATFE can decide that a mere bayonet lug is a dangerous item that is verboten , do you really think there is any limit to what they can legislate out of existence?
      Lets play it cool, and keep the lingo on the DL.

  • Rip May 27, 2014, 9:31 am

    Coice of words are key. The arm brace idea is kool. Why didn’t you show how that working instead of running with the improvised sbr bullshit. People will figure things out on there own.

  • Duh May 27, 2014, 9:00 am

    The best thing for the gun community you could do is to remove this article from your server. New products and promotion thereof has been used as fuel for the wrong reasons. ie, the AK pistol from Olympic Arms and the once cherished importation of steel core Norinco 7.62 x 39 ammo. That ammo was banned because of the pistol which never even came to market. Only hype was enough. Like this article…

    • Administrator May 27, 2014, 9:09 am

      Ok so this is the silliest yet. Are you guys really taking that much Zoloft? An SBR is a legal term. Do you really think that the overbloated BATFE under Holder doesn’t see that this looks an aweful lot like an SBR. There have been several letters from them confirming that this is not considered an SBR, period. What people call it has no bearing. Like the SlideFire, they would have to change a body of law to restrict this device.

      The AK pistol dates back to the Clinton gun ban. I have one of the first ever made actually. It came with a 75 rd drum welded onto it. And apparently you think the steel core importation ban came because of gun writer saying wow this is cool it can shoot through police shields? Maybe it isn’t nice to snipe at people about their Zoloft addiction, but can anyone else come up with an explanation for all of this silliness? All of these decisions come from the top, and they only use their shills to read GunsAmerica Magazine.

      • Chuck Backus May 27, 2014, 12:03 pm

        I agree with all the others that say you must be careful how you word your article. “length of Pull” is not appropriate for a forearm brace, period! The O’Taker and Holdumb administration is unlawful in all that they do with regards to our 2nd Amendments rights. Why give them, and others, more reason to take away whatever they can…….good article tho. I have a DB15P with the Sig Brace, and every time I go to the range the first question is “do you have your ATF stamp?” Lets not use words that will piss off the rules makers. Common sense and discretion must dominate the conversation, OK??!!

  • Rob May 27, 2014, 8:38 am

    Agree with the other comments. Leave it alone. It is a brace. Cut the SBR crap and there is no length of pull on an armbrace. Mess with it too much and you screw up a good thing. Anything designed to adjust “length of pull “most likely converts it to be used from the shoulder thus making it a stock. Leave it alone.

  • matt May 27, 2014, 7:15 am

    Austin has THAT right.. I’m not for walking on eggshells with the libtards, but with MACs video (and many others) and this is probably the 25th article I’ve read on it ALL calling it that.. it’s only a matter of time before you rattle the ATFs cage enough for them to change their mind.. Lord knows they’ve done it before!

  • 82nd black rifle squad May 27, 2014, 7:03 am

    Nice improvised stock/sbr! I am definitely going to get me one for every caliber ar pistol I own plus 1ea for spares…

  • Ken May 27, 2014, 5:56 am

    I agree with Austin. STOP calling it an SBR or improvised stock. Article IS very good BUT it is NOT an improvised stock or SBR!
    I will not be surprised if the BATF eventually implements new rules/ laws (like we need more), as a result of ………. well, you know what I mean.

  • Matt Janes May 27, 2014, 4:54 am

    You are king of the obvious! Why must we always eat our own and give the anti crowd more published fuel for the fire?! Editor…ditto. It’s a handgun arm brace…period! It has no other purposes. ..period

  • Austin May 21, 2014, 10:31 am

    Stop calling it an improvised SBR or improvised stock. You’re not doing us any favors by saying things like that.

    Other than that, good review for a great product.

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