The following, quoted from one of mhb's posts on another forum, may help us understand the difficulty he is having adapting to the unfamiliar SMLE -

"Some of the information in CPT Laidlericon's excerpt is a bit confusing: 'CHS', though obviously related to headspace, is not explained, though 'GO' and 'NO-GO' limits are clear enough; the '.050" limit' referenced is unexplained, and not self-explanatory. The permissible degree of over-rotation of the bolt head is interesting, but only useful it there are a number of candidate bolt heads to work with. . .
I was unaware of the need for the rear of the bolt head shank to contact the firing pin collar before the head is fully turned-in to the bolt body: is this critical in some way? If so, it would seem that it could be achieved (if not currently present in the assembled bolt) by increasing the firing pin protrusion until contact is achieved, and then shortening the protruding tip of the pin as necessary."

(View in context at Lithgow stock finish... - Page 3 )