The Rem 700 Leupold QD bases will fit your M77. The issue is the where the front scope ring ends up. The back ring wouldn't cause issues ejecting cases but the front ring was a problem with the extended base mounted either direction. I looked at a couple of other M77's and the Warne mount puts the rings in the right place. Weaver makes a set of aluminum mounts that I won't use, particularly on a large magnum caliber rifle like my 7mm Remington Magnum. Using a vintage Weaver "El Pasoo" 40mm scope, the low height rings work for me.