tried unique, hero, hs6, 4227, 110, 1680 4198 335 exterminator, tac, on the faster side 4895, 4064, re17 and re19 for mid range powders and re25, and 860 on the slow side. Ones that came the closest have been re19, re25 and 4895. the two reloader powders are just to dirty burning so still the closest thing to success is 4895. the 300 blackout probably isn't going to take as much to insure reliable chambering as its got loads with fairly clean burning powders so the chamber doesn't get all crudded up in a few rounds. That and it gums the heck out of the trigger mechanism so bad that you about have to pull it apart and clean it because spray cleaners do get it all