my well used and much loved Renegade is a 1:48 twist. originally designed for conicals (and a thingy called REAL- Rifling Engraved at Loading, a conical with bands on it which is fired without a patch) this was said to be the next best thing for deer in the newly established ML season dusing the '60s and '70s... that's right, sonny, long ago when men were men and when giants walked the earth...
being an inveterate cheapskate, i tried PRB in mine and, although the barrel's rate of twist is something of a compromise between PRB and conical, the PRBs work fine. i don't think i've launched a conical in the last two decades.
there is a 'sweet spot' where the rate of twist, the weight of the projectile and the muzzle velocity and the speed of the ball's spin all form some sort of cool harmonic, and you get the smallest groups. (Avagadro's number and the phase of the moon are probably in this equation somewhere, too: my math isn't strong enough to cope with more than about a half dozen variables). anyway, when you find this 'sweet spot,' your groups will tighten and if you use a smaller or heavier charge, they will open back up. i have read that if you have a slower rate of twist, your sweet spot will be bigger, and you will have a greater range of possible loadings. my 1:48 twist barrel doesn't like more than about three to five grains more or less, but i've neen told that so- called "roundball barrels" with twist rates as slow as 1:72, will let you get away with a variance of eight to ten grains and still pattern well. i haven't any personal experience with this, so take heresay with a grain of salt.
you should get minute of bambi with your 1:48 twist, with no problem. practice, of course, is much more important than equipment.