The Strike Industries AR-15 Pistol Buffer Tube Kit can be used with a 300 Blackout pistol. The Strike Industries AR-15 Pistol Buffer Tube Kit will work with any Mil-Spec AR15 lower, so as long as your lower receiver is Mil-Spec it will work.
This is a shortened buffer tube, at just over 5" this buffer tube reduces the overall length of an AR pistol.
This will work just fine with any barrel length on any standard .223/5.56 AR lower.
Our Spre Slick has an outer diameter of 1.247". From SB tactical's product page it looks like the SB MINI will install to tubes up to 1.25". You will be good to go.
The Strike Industries Pistol Buffer Tube is shorter then the standard AR Buffer tubes so you will need to use the included spring and buffer. Since you plan on using the tube on a 9mm we suggest you purchase the Strike Industriess 9mm AR buffer designed to work specifically with SI pistol buffer tube.
https://www.opticsplanet.com/strike-industries-ar-pdw-9mm-buffer.html
The Strike Industries AR-15 Pistol Buffer Tube Kit itself will remain a pistol as this is simply a shortened buffer tube.
Our SPRE SLICK was designed to be used on an AR15 .223/5.56 platform.
The Strike Industries AR-15 Pistol Buffer Tube Kit can be used with any brace that will work with a 1.247" outer diameter tube. Strike Industries is also developing a brace specifically designed to be used with this tube.
The Strike Industries AR-15 Pistol Buffer Tube Kit will not work with a standard carbine buffer.
The Strike Industries AR-15 Pistol Buffer Tube Kit can be used with a 9mm AR pistol.