Sometimes the press wins, and sometimes the case wins. If the sizing die is setup without firm contact between the shell holder and the die (cam over), variations in the slop in the press, brass hardness, case lube, etc. can cause the cartridge case to datum (bump) to vary considerably.
My...
As I understand, you were previously setting up to full length size, as recommended by manufacturers, by turning the die in to touch the shell holder plus about 1/4 turn. Now you intend to "bump" the shoulder some amount compared to a fired case.
In the interest of reliable chambering in the...