A removable optical sight mount adapted for use with a military-style rifle such as an M1A provides a centrally aligned support projecting well to the rear for use with sights having very limited eye relief. The removable sight advantageously uses a three point lock up or attachment to the rifle, the three points being (1) an elongated longitudinal tenon engaging a groove on the left side of the rifle secured with a fastener and cammed into tight engagement with the groove, (2) a transverse rear guide block, and (3) an adjustable front set screw that, when tightened, bears on the rifle receiver's crown.