I play with 300 Blackout extensively and have done tons of videos on Youtube for it. The link to my playlist is below:
https://www.youtube.com/@wanneroo7106/playlistsClick on the 300 Blackout tab on the page. I've got over 30 videos in there with multiple loading projects going on. Currently am working on "Project Big Booty", a 300 Blackout subsonic loading project. The 4th video in that series is dropping soon and then a brief 5th video to wrap the project. I used CFE BLK and 220g Berrys Bullets for that project. I have other 300 Blackout projects that will be coming up on the channel with different bullets and powders.
When I do a project on the channel I do an introductory video where I explain what powder and bullet combo I am using and why. The next videos I go through things I learn along the way, answer questions/comments from viewers, get chrono data and do some accuracy testing. And I will do that until I achieve a final load I am satisfied with.
The Hornady 110g Vmax bullet project with Winchester 296(Hodgdon H110) I got up to 2500 FPS which matches a 7.62x39.
One of my favorite bullets for 300 Blackout plinking is the Hornady 150g FMJ. These are cheap and shoot well to 100 yards.
300 Blackout works with any magnum pistol powder. IMR 4227, Lil Gun, H110/W296, A1680 and others made by Vihtavouri and Lovex.
The nice thing with 300 Blackout is you can use just about any .308 bullet out there and you are shooting it out of a .223 sized action. It's a very useful short range cartridge.
Brass, yes you can cut down .223 brass and reform it and I have some of that but I prefer factory 300 BO brass. I like Starline Brass as it's great quality for not an outrageous price.
I use 16 inch barrel AR semi autos for everything but will add a bolt gun at some point to the mix.
I love 300 Blackout, I have more fun with it than any other cartridge.