In my 6.5/284 I use Winchester 780 supreme for a 140 A-Max load, probably a bit hard on the throat but good velocity and accuracy in my rifle. The other powder I have used which seemed good was 2213sc ADI with nosler partitions, the hand loaders guide from 6mm Ackley will give you an idea on where to start. Sorry can't help with the 22/250.
Cheers.
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