I got a Rem in 221 Fireball with a 1:14" rate of twist, 24" barrel. what's the largest bullet weights I can accurately fire? I am looking into 55-65 gr bullets.

55gr bullets will likely be the heaviest the 221 will stabilize, and if the 55gr is "long for weight (Vmax style)", those may be iffy.
I've never shot heavier than 50-52gr in mine, due to the velocity I desire.
But the 22-250 typically runs a 1:14 twist, and even with their speed, 60gr pills are about as heavy as they stabilize.

Greg

great info Greg, your information corroborates what Remington has told me. I am strictly a hunter so match bullets are not in my radar. Many thanks

My daughters 221 works well with the 50 gr hornady v-max. I tried the barnes 53 tsx and accuracy wasn't so good.

I think you'll find the small case capacity and mild twist rate limit you to 50 and possibly 55 gr bullets. Someday I'll have to try some 55 fmj's out of curiosity.

My 1-in-16 twist hornet shoots 60gr Hornady SP's just fine. It likes Sierra 55gr SMP's and Hornady 55gr SP's too. The 55gr Hornday SP's kill feral goats very effectively and the 60gr Hornady's work very well on hares - better than 55gr Hornady's. The heavier bullet keeps it's velocity better but doesn't shoot quite as flat. The 55gr SPcann's are cheaper so that's what I use.