I recently acquired an AR-15 upper in 300 blackout and want to start loading for it. It's a 16" barrel with a pistol length gas system. I want to cast heavy bullets for subsonic loads for it. I use hi-tek coating on my cast bullets. So I'm looking for recommendations on molds for this bullet and powders to use with this bullet in subsonic loads. I've done some searching of threads here and couldn't seem to find quite what I was looking for. Thanks in advance for the input.