Not sure if any of this information helps, but just going to toss it out there.

I've had three different 300 Blackout rifles and just couldn't really get into them. That being said, I'm in the process of putting together a pistol in that caliber and I'm feeling pretty excited about it. I figure it should make a sweet little CQB firearm. Especially once it gets officially SBR'd and suppressed.
I'm set up to load for the 300 though so I don't have concerns with the ammo.