Thread: Trailboss, 151gr cast hollow points and 300blk

Work out case capacity with bullet seated (mark depth of projectile). Fill with TB to mark, multiply by 0.7. Load this calculated charge, and work out whether it's sub or supersonic (either with chrony, or I assume you have a suppressor to go by ear). Drop in say 0.2gr increments, until it's just going subsonic, then drop 0.1-0.2gr below that to allow for temp/pressure/altitude differences. Trying to work out what makes the same projectile go a certain speed in a different cartridge and replicating that isn't the way to go about it..