I think a better idea is to ream the 22-250 out to Ackley Improved.
That will give you as much power and it will give you a straight case,
which has advantages, like less brass flow, handles pressure better,
puts less load on the bolt.

I think the 220 is slimmer, so I don't see how you could ream the
22-250 case to be the smaller diameter of the swift.

links:
https://en.wikipedia.org/wiki/.220_Swift
https://en.wikipedia.org/wiki/.22-250_Remington

220 base diameter= .445 in
22-250 base diameter = .469