Also, Jeff Bartlett at gibrass.com has milsurp powder for cheap. I figured out a way to duplex BR-5 with IMR 7383 to get it to cycle my AR- 15 in 300 blackout. Cost per round with 230 gr. cast boolits is $0.05.
https://www.youtube.com/watch?v=EdxzWY3_o0g&t=845s