GL,
I have a CZ527 Varmint HS with a 1/9 twist and it shoots the 75 a-max very accurately. The 221 is a factory CZ 527 American with a 1/12 twist and I just could not believe the performance I got when first tried the 60 V-max. 40 V-max makes a "whaaap" sound and the 60's make a "WHOP" sound upon meeting a prairie dog. Quite a distinctive difference in sound. Terminal "show"
on is on an upper-level above the 40's, also.
Sounds like going to the trouble to get heavier (than 60's) bullets to shoot well sith the 221 FB may not be worth it. I really thought someone on this site may have already tied this and could relate their experiences.
Thanks for the responses.
Bill