Some of the early rifles used by the Marines in 1966 were M70s and M700s bought at the PX on a stopover in the trip to Vietnam.
They used Redfield 3-9x40, some with AccuTrak reticle. Fixed Redfield, Weaver, and Unertl target scopes were soon in use.
7.62 NATO, .30-06, and .300 Win Mag were used.
You will see M70s and 1903s wearing heavy walnut target stocks.