Sixgun,
Glad to hear that those bullets worked out well for you. I do not have any experience with the 55gr. RCBS but since it is in same weight range, I would think that it would perform similarily in the same velocity range.
Since a 55 gr. bullet is heavy for the typical twist in a .22 Hornet bbl, you will probably find that velocity will need to be at least 1,500 f.p.s. to get consistant accuracy. At least that was the case with my Win. '43.
3.8 /231 /CCI 500 gave 1,659 f.p.s. with a 55 gr. NEI bullet and 1,603 f.p.s. with the 59 gr. 225462 in my '43's 24" barrel.
With regards to gas checks, for best accuracy, you will probably definitely need them at those velocities with fast burning powders, but it never hurts to try. I get good accuracy with a lighter 45 gr. cast bullet w/o the gas check at 1,500 f.p.s., but not quite as good as with a gas check.
w30wcf