My first .22-250 was a Ruger, though it was an M77 tanger, not a #1. 40 grains of H380, 50 grain hornady SX, WW brass, and Fed 210m primers. Half inch. A more recent .22-250 really liked Varget with Speer 50 grain TNT and those Hornady 50 grain SX bullets. I have not had a lot of luck with 55s, especially the longer polymer tipped bullets, in a 1-14" twist. (Exception was a Swift with a PacNor barrel.)
The only #1 I've gotten to shoot consistently sub MOA was a .375 H&H stainless. I've gotten a couple others down near MOA. You can help a good bit by adding a set screw between the forend hanger and the barrel to maintain constant tension there and dampen the vibrations that come as the main spring drives the hammer. Often that will fix vertical stringing.
Tom
