Here is your answer courtesy of Fred Moreo at Sharpshooter Supply....
Receiver Changes
For 2003, Savage introduced their new ACCU-TRIGGER models. Besides the trigger change, the receiver now has a round top in the rear scope base area. It will utilize the same base in the rear as in the front. The Weaver #46 base will fit both ends as well as the #402 extension base if you have a need for mounting extremely long or short tube scopes.