While the KAK Shockwave Buffer Tube Kit SHOCKWAVE-TUBE-KIT will fit your build, it may be a good idea to use a slightly heavier buffer. Due to your shorter barrel, and shooting 300 Blackout, a heavier buffer may be needed to help the gun cycle properly and reduce recoil impulse. I will link an H3 buffer that I recommend below. If you have anymore questions, feel free to email us at Techsales@opticsplanet.com.
https://www.opticsplanet.com/kaw-valley-precision-heavy-tungsten-h3-carbine-buffer.html