I have a document put out by the USMC.
It's document number is TI-02648A-25/10B
USMC Technical Instruction,Match condition procedures, Rifle 7.62 mm, M14
HQ USMC Washington, DC 20880
27 November 1972
It gives EXACTLY how to modify the M14 for "Match Conditions". While I readily admit this isn't the 'Sniper Information' you requested, its as good a place as any to start. Jim