Your saying you keep the 6.5 CM because it was more accurate then the 6.5 PRC Right ? Well the rifle controls the accuracy! NOT the Cartridge ! So would you have keep the 6.5 PRC if it shot more accurate ? RJ
WRONG!
IF that were true then cases like the 6PPC and 6BR wouldn't absolutely dominate Benchrest competition. There are most definitely features of the cartridge case that increase accuracy.
The 65CR has a very long neck and a relatively flat shoulder angle. Those two things increase accuracy over a shorter neck and more sloped shoulder. The shape and length of the powder column also contribute to accuracy. Typically shorter, wider powder column is more accurate than a long, thin one.