Just remember velocity alone wont kill any prairie dogs. The a i version 22/250 with 69 gr bullets can put a hurt on them out to 600 or so with no problem.
From that point your far better off with a 6mm than you would be with a hot rod 22 for prairie dogs. I have a 17 rem center fire that sends 25 gr pills at lightning
speeds also. It stays home in favor of my 223 when i go p dog hunting. So do 40 gr bullets for the 223. Mind you scaring them can be fun also, but hitting them
is really what its about. Id rebarrel the Rem to 243 ai or 6 mm rem ai or a 6/284.