I have been involved in the 300 Blackout for a VERY, VERY long time. Right after my helicopter accident I dabbled in bullet design as well as making bolt lift kits as a means to occupy my time and forget about life for a while. During that time I designed three different bullets for the Blackout. First was a 245 grain bullet that is super popular. Second was a 129 grain pointed bullet everyone dubbed the "Crayola of Death" because it looked like a Crayola Crayon. And initially it did not seem to work with harder alloys and slower twists it seems to do fine. And my final is the heaviest cast bullet available for the 300 Blackout. It is 265 grains and is stable in 8 twist or faster at subsonic velocities and stable in a 10 twist at above 1,100 fps. I licensed it to ACME bullet company and they produce and sell them. If the OP, or anyone else, gives them a try I will gladly provide load data for the bullet. It, unlike other subsonic bullets, hits HARD. I get feedback regularly from hunters and it smashes through shoulders and skulls even at subsonic velocities. It will feed from a magazine and cycle in an AR.

http://www.acmebullet.com/bullets-re...0Out/Black-Out

The "DS" in DS Special is my screen name.