tinker,

A lot of doubles will regulate with lighter loads and lighter bullets.

One's I can think of are:-

9.3 x 74R

375's H&H and Flanged Magnum - I haven't / didn't try with my 375 2 1/2"

The various 450's - I have tried 500/450, Rigby 450 3 1/4" and obviously others have tried
450 No 2.

450/400 of all persuasions will do it

500 Nitro's will all do it.

500 Nitro