Near of Alberta makes a once piece scope mount out of steel.

Would that work on a 416 Rem on a mid-weight rifle?

Rail would be handy if scope dimensions present positioning issues.

http://www.nearmfg.com/products.htm

No issues with Leupold rings and 2 piece bases on my .416 RM.

Steel or aluminum would work, what does makes NEAR very nice is they have a recoil shoulder machined in the mount that butts up against the rear of the front receiver ring. If you're worried about movement you could always pin any one piece mount with 1/8" dowels between the front and rear screws.

The .416 isn't brutal on rings or scopes..I like Talley QDs. Leupold QD, and Ive had good luck with those cheap Weaver rings and bases on big bores..Control are nice...I wouldn't worry about the capabilities of rings and bases on a 416, Id pick whats available and what looked good to me...That said its not a mistake to use 8/40 torxs in any rifle receiver, even a varmint rifle. I call it cheap insurance, there are more scopes knocked out of zero on trees, rocks trucks etc than recoil.

When you get to the 458 Lott then its time to start considering the recoil with both scopes and the mounting system.