603country, your tests are interesting.
Did you have both the full length bushing and standard dies set to bump fired case shoulders back only a thousandth or two? If more that that, it often causes accuracy problems.
I only hope the variables you introduced into the results are small. But you're off to a good start in testing.
You might try On Target software (free download) then use it to measure your groups' mean radius. That's about the best way to measure shot groups and ends up telling you what the average distance is you'll miss your point of aim.
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