Brad, from what I can find the "S.A.CO. .303 SAV." head stamp was used by Savage from 1914 to 1917 (depending on how much inventory was on hand when they switched from "CO." to "Corp.". From 1898 to 1914 it was "S.A.CO. .303".
Savage loaded their own ammo till around 1928 (maybe 1934). The early Savage ammo boxes state that the ammo was loaded with Savage brand powder. I don't think Savage ever made powder or primers they just purchased from other makers. The "S" marked primers are thought to be from Union Cap & Chemical CO. as "S" marked primers have been found mixed in their primer tins.
