Rim Space British Armourer Rim Space Guage Sizes Reference Size Bolt Head Length Savage and Long Branch No4mk1* Chamfers Video! North American Myths Fitting Sequence Cocking piece grooves and safety lug Half Cock Lock Striker Spring Winding & Bolt Handle Lift Armourers letter punching the striker threads Safety group interaction Video! The British 303 cartridge of all ages are head spaced on the rim – really a rim space, which is inter-changed with the bolt head for one wit