I have been watching KAK with a lot of interest since they came out with their original Sig SB-15 Pistol Brace specific buffer tube, the KAK AR-15 SIG SB-15 Pistol Buffer Tube. One thing kept me from trying that buffer tube and that was its requirement to use a modified end plate. Apparently I am not the only one who felt this way and, obviously, I am going to have build another AR pistol because they have now released the KAK SUPER SIG SB-15 Pistol Buffer Tube which has a more streamlined design than the original, is slightly longer (a good thing for AR pistols), and uses a completely standard castle nut and end plate.
It retains the shoulder feature of the original. This shoulder is machined into the tube and is the key to the KAK SUPER SIG SB-15 Pistol Buffer Tube’s functionality. It serves as a hard stop to prevent the SB-15 from sliding forward. It also serves as a stop for the spacers that KAK is now offering to be used to adjust the length of pull of your SB-15.
If you are building an AR pistol and intend to use an SB-15 Not-A-Stock, check out the KAK SUPER SIG SB-15 Pistol Buffer Tube.