My T/C 1:48 50 cal shoots round balls extremely well too. It also like the 250 gr R.E.A.L. bullet.
Green Mtn. makes a drop in barrel with a 1:28 twist which would be better used with conicals. Mine likes the 275 gr Maxi hunters. I just never had too much luck with saboted bullets. the 245 gr. Powerbelts were just OK.