What specific ammo? Bullet diameter is important too. Did you work up the load with the milsurp ball? Lotta that is really low end stuff though. Not made for accuracy.
Those shims were put there for a reason. However, it'd only apply to the scope and mounts used at that time. Not whatever scope and mounts Century cobbled together.
Mind you, I'd be suspicious of any rifle Century had anything to do with.