Depending on how much smaller a full length sized case is in volume than a neck only sized one, there can be as little as a 1% change in capacity. Few, if any, full length sizing dies return a case to its original, new and unfired dimensions. And in my experience, new cases give better accuracy than neck only sized ones.
I agree that doing your own testing is the only way to know.
But run the same test a few times. If the results are not within 10% of each other, it's not a good test. Good tests of rifle and ammo accuracy give close to (within 10%) the same results all the time.
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
Last edited by Bart B.; September 28, 2013 at 08:55 AM.