Many have seen the SIG arm brace by now, but have you seen the dedicated pistol buffer tube made for it?
The world of AR-15 pistols took a turn recently when the ATF ruled the addition of a SIG brace to an AR pistol buffer tube does not deem the firearm an SBR. In addition the ATF added that it is not illegal to shoulder the SIG brace when shooting. AR Pistol owners have been rejoicing ever since.
While the SIG brace is an awesome addition to any AR Pistol, the KAK Industry SUPER SIG SB-15 buffer tube made specifically for the SIG brace makes a world of difference for the shooter.
KAK Industry is located in Lees Summit, MO and specializes in the design and manufacturing of wildcat uppers for the LR-308 platform and AR15. I spoke to KAK founder Kurt Kosman’s who shared his roots and passion for making wildcat parts such as barrels and uppers in 358 Winchester, 350-300 WSM, 375-300 WSM, 450 Marlin and 458 SOCOM. “It is our specialty and what we do best”, said Kosman.
Enough about KAK, lets talk about the real reason we are here. The SIG SB-15 pistol buffer tube is a dedicated tube designed to work exclusively with the SIG Brace. The patent pending tube was designed to be a perfect fit for the Sig arm brace and provides a shoulder for the brace to rest up against, giving the shooter a longer length of pull.
The mil-spec anodized tube weighs only 6.2-ounces and is 8.45” long from the end-plate.
Installing the tube was fairly straight forward as it screws directly into the lower receiver just like any AR buffer tube. The tube utilizes a standard carbine buffer and spring just like any mil-spec or commercial buffer tube. Installation took about 15 minutes and was really easy. You will need a castle nut tool to tighten the castle nut.
The Sig brace slid on with a decent amount of pressure required to fit it in place. This is a good thing as you don’t want it walking around while shooting. I was a little concerned that the anti-rotation tab found on the SIG brace no longer locks into the end-pate and that it might cause the brace to move, loosen or rotate when shooting. To date we have put hundreds of rounds down range with this setup and the brace has yet to walk on the tube. That being said, it is still a concern I have. I have not heard anyone complain of walking issues, but I thought I would mention it just in case.
I am enjoying having a dedicated tube for the SIG brace and have since bought a few of KAK’s standard pistol buffer tubes to use on my pistol builds. This is a must have if you are going to run the SIG brace on your AR pistol.
As of this writing, the tube is available as a kit (sig tube, castle nut, QD endplate, buffer and spring) for $93 or as a stand-alone tube for $42. KAK also makes a spacer kit to extend the tube as well as FDE and OD green versions. You can find more information on the buffer tube here.
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