ilikeoldguns
1. If the decapping rod/expander button is screwed down too far it will stop the case from entering into the die and stop short. The decapping pin should should only be protruding 3/16 of an inch from the bottom of the die when properly adjusted.
2. "DO NOT" screw the full length resizing die down to contact the shell holder and allow the press to cam over on a British .303 case. If you do this you will OVER RESIZE the case, shorten its life and cause case head separations.
Below is a Wilson case gauge with a fired .303 British resting in the gauge, the amount the case is sticking above the top of the gauge is how much longer the military chamber is from SAAMI civilian standards. If you adjust the die to contact the shell holder you will bump the shoulder of the case back too far by the amount sticking above the case gauge.
Over resizing the British .303 case will cause the case to stretch and thin in the base web area and cause the case to fail due to a case head separation. The military Enfield chamber is larger in diameter and longer than civilian SAAMI standards and you need to compensate for the longer chamber.
Once the case has been fired you want the case to headspace on the shoulder of the case and NOT the rim. this will prevent the case from stretching and thinning in the base web area. What you really need is a neck sizing die to extend case life or only "PARTIALLY" resize the case with a full length resizing die. Meaning you will have at least 1/8 of an inch air space between the shell holder and the bottom of the die with the ram fully extended.
By neck sizing only the shoulder of the case will hold the base of the case against the bolt face and the case has no room to stretch.
Head clearance is the "air space" between the bolt face and the rear of the case. Excess head clearance will shorten the life of any reloaded cartridge case.
All military chambers are fatter and longer than there civilian counterparts and the correct shoulder bump is critical for long case life. Below with minimum head clearance the case will stretch to meet the bolt face and then try to spring back to its original length. When the head clearance is too great the brass will stretch and thin beyond the elastic limits of the brass. On a bolt action rifle you only want to bump the shoulder of the case back .001 to .002 and .002 to .004 on a semiautomatic rifle.