I'm wanting to put together an AR-15 in .300 Blackout. Has anyone got information on the do's and don't of that caliber. Has anyone actually done it here. I've done some reading and it seems like the caliber I've been looking for. 1. Deer capable 2. Medium size case that will feed from a standard AR magazine. 3. Easily obtainable brass that can be made from .223 brass. 4. Standard .30 cal bullets. Seems like the perfect caliber to me.