tank1949, how many shots are you putting in each test group?
If you shoot several groups with the same load and they're not all the same size within a 10% spread, you're not putting enough bullets into each one for them to be at least 90% valid.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master