SIG Sauer’s SB15 arm brace has radically changed the AR-15 market, accelerating the adoption of AR-15 pistols everywhere. Designed to make shooting AR pistols one-handed easy, they can also be shouldered more-or-less comfortably and more importantly legally, giving SB15 users some of the look and feel of short-barreled rifles without the hassle of jumping into the world of National Firearms Act-regulated items.
It’s not adjustable, it’s a little flimsy and it’s on the short side but it works, both as intended and as an SBR-lite alternative, and people everywhere are getting in on that sweet SB15 action, not just SIG who offers a handful of rifle-pattern pistols with SB15 pistol braces.
To shore up some of the pistol brace’s shortcomings two companies have developed SB15-specific pistol buffer tubes: KAK Industry and Phase 5 Weapon Systems. These companies have developed longer buffer tubes tailor-fit for the SB15.
KAK has several pistol buffer tubes made for the pistol brace, the KAK SIG Pistol Buffer Tube and the KAK Super SIG Pistol Buffer Tube.
These pistol buffer tubes are extended to lets users hold their pistol a little further away from their chests when firing them while shouldered. This gives them the reach to make shooting more comfortable than when the brace is installed on a standard pistol buffer assembly.
The original KAK SIG Pistol Buffer Tube has a thick, straight extension on the tube that stops an installed brace from slipping forward down the buffer tube, while the Super model has a swept, machined extension.
A simpler design, the standard KAK tube runs just $32 by itself. KAK Industry offers discounts for bulk buys as well as packaged as complete buffer assembly kits including the recoil spring, buffer and endplate. These kits are priced at $58 with a standard endplate and $78 with a quick-detach sling point endplate.
The tapered Super model starts at $42 for the basic tube. Like the basic version it’s also offered with kits for $73 and $93 with plain endplates and Q.D. sling point endplates respectively. The basic model screws right into the buffer tower while the Super has an anti-rotation index and installs using a castle nut like a carbine buffer tube.
Phase 5 carries just one SIG SB15 buffer tube but it’s a cool one. Like the KAK models it holds the brace out a little further from the upper receiver, but it is not an extended buffer tube.
The Phase 5 Hex2 is a pistol-length buffer tube with a long hexagonal extension that runs about halfway down the length of the tube. This acts as a stop for a SB15 brace or standard buffer tube cover.
The hexagonal extension is a perfect match for the SB15, though, which hangs off the tube by a short amount. Taking advantage of this cavity, Phase 5 includes a tube cap that lets users store accessories in the brace like a rifle stock. This compartment can be used to stow a bottle of lubricant, a pull-through cleaning kit, batteries, a bolt repair kit or whatever else a user might want to pair with their pistol.
The Hex 2 mounts like a standard carbine buffer tube with an index and a castle nut, like the KAK Super tube. One nice little addition to the Hex 2 is an anti-tilt extension at the base of the buffer tube for use with gas piston systems. Most modern gas piston setups are relatively tilt-free but this is a nice extra touch of insurance.
Priced at $60 the Hex 2 is also very appealing. It comes with an endplate, a castle nut, storage compartment insert and a nitrile foam buffer tube cover. All that’s needed is a buffer and action spring.
If you’re building a pistol buffer with a SIG Sauer SB15 pistol brace then put KAK Industry and Phase 5 Weapon Systems on your short list of buffer tube manufacturers. These are perfect for all SB15 builds and won’t break the bank.