I agree with the others, a slower powder, such as 4350, 4831, etc.
Shoot at 100 yards. Get lots of targets. Shoot each different load at a clean fresh target for groups. I use targets printed off the computer, cheap paper and lots of them. I also keep all of these targets in a binder to compare later. Do your shooting at the range. Do your homework, research, loading, and measuring at home. That way you don't get stressed out about group size while you ar still shooting, just concentrate on shooting.