A full length resizing die is designed to make a fired case at "LEAST" .002 shorter than the GO gauge, I have a Lyman die that will make a .223 case .006 shorter than minimum GO headspace. Using a resized cartridge case for a GO gauge can have adverse effects, one of which is "NOT" being able to push the shoulder back far enough to chamber "YOUR" fired rounds.

Buy and use a GO gauge to set your headspace and you will always have a zero baseline when using any cartridge headspace gauge to tell you "the short and long of it"