Re: M40 Original scope question
THE USMC never used the Accu-Trac series of Redfield scopes on their contract M40 sniper rifles. They only used the 3-9x Accu-Range model with the "Traditional" round lenses. They were not the "Widefield" models which weren't introduced until 1971. AFAIK, Redfield didn't introduce the Accu-Trac feature until 1978.
The Accu-Trac models had a BDC elevation turret in addition to the "tombstone' range finder. The idea on the Accu-Trac was to bracket the target with the horizontal crosswire stadia using the tombstone scale to indicate the range, then dial the indicated range with the BDC elevation turret. The Accu-Range scopes were equipped with Redfields standard hunting style turrets with no BDC feature. The Accu-Range and Accu-Trac models are often confused and some folks use these names interchangably, but the Corps only used the Accu-Range scopes as standard issue with the M40 rifle.
I'm quite sure that some Accu-Trac scopes were employed at some time by by Marines, but these scopes would more than likely have been private purchases from either the PX or from sporting goods stores.