I am happy to be corrected but the differences between the two cases doesn't amount to much. The rims are thinner on the 5.6 by something like 0.010" and the shoulder of the Hornet is a little further forward. I "think" the twist and bore are the same as the early Hornet at 0.223". Any of the 40-45 gr. or so Hornet bullets should work well. I shoot cast out of my Vierling.