With conicals there is the problem of finding the right sabot or patching material and the accuracy is not great anyhow.
A conical is not a sabot, and conicals are loaded without patching materials. Conicals are a slight variation on the 19th century minnie ball. 1:48 twist will stabilize T/C Maxi Balls and Maxi Hunters, as well as Buffalo brand conicals. Lee makes molds for conicals, that are known to have great accuracy, and the Lee Enfield Caplock rifled musket of the Civil War era was, and in reproductions is, a very accurate rifle..., using a slower twist..., although it's .58.
The key to a good conical is to get one that is very close fitting. It should require a little bit of pressure to push it down the bore. When the charge is fired, the pressure deforms the base, which pushes against the rifling and imparts spin and seals gases. When you have accuracy problems, it can be from improper twist rate..., but more often it's from an improperly fitted bullet that has too much room and so doesn't consistently seal or spin.
The Hornady bullet shown above has a hollow base, just like the Civil War Minnie Ball, which makes it easier for the gases to seal the bullet against the rifling. The CVA Powerbelt bullets have a plastic collar on the base, similar to the old "gas check" used on modern lead projectiles. The idea is the same. Seal the gases in and impart spin to the projectile.
Unless you are going for very large game, patched round ball is plenty. Remember you will get heavier recoil when using a heavier projectile, and the deer often don't know the difference between 180 grains of lead, and 350 grains of lead. You though, will.
LD