Perhaps my "good" results are due to the hardness of my alloys? I use boolits that measure Bhn 11, which I cast myself and adjust my alloys to reach that by the use of a Saeco hardness tester. It seems to me that a lot of folks run into leading and accuracy problems with diameters due to their use of commercial or home grown "hardcast" or quench cast boolits, whatever "hardcast" is defined to be.
I've always maintained that shooting cast boolits ain't a science, it's an art, and I'm still learning after playing around with them for 48 years!