I started at 24gr. of RL10 for 223 for the 30's and ran out of case capacity as I worked up. Guat brass BR-4 and 71/2's primers, I Also have some 4198 loads worked up started at 23gr. and am past that a good ways. Same brass and primers. Both loads shot well on the warm end also, out of 1-9 twist AR's and Savage fv, also through 1-12 Rem.twist.
In 22-250 I Started at 34gr. of RL10 with the 30's, also I'm well past that.
Win. neck sized brass, Fed Match primers. I'll not waste my time try'n different powders as I;ve found a RL10 load for it.
I've seen loads posted for 4000fps. in the 221FB. The bullet will handle all the speed your case/pressure can muster. Does'nt come apart, If you look around you'll see loads posted for the 220 Swift over 5000fps.also.