Firing pin protrusion is .040 to .050 and you also have bolt head timing to contend with or when the bolt head contacts the collar on the firing pin and starts pushing the cocking piece to the rear. The rear of the firing pin should be flush with the rear of the cocking piece.
Read the Canadian No.4 Manuals below for more info.
No.4 Enfield Maintenance Instructions dated June 28 1991
No.4 Enfield Operating Instructions dated July 15 1991