Although muzzleloading rifles may be found in .45-, .54-, and even .36- and .52 calibers, the most common hunting caliber is .50. The “half-inch” bore is the most flexible in terms of loads, has sufficient power potential for commonly hunted game, and offers the widest accessibility of support and maintenance equipment.
A large part of the reason for the change is the development of popular pellets (Pyrodex was first) manufactured in 50-, 30- and 20-grain capsule units.
For whitetail deer hunting, in-lines with a 1-turn-in-24 inches to 1-28 twist will deliver excellent performance with a 100-grain propellant charge and sabots in the 250- to 300-grain range. Conicals in the 300- to 385-grain range typically do very well with a similar powder charge.
A .50-caliber muzzleloader with a 1-32 to 1-38 twist rate should do well with the same sabots and conicals with a propellant charge in the 85- to 90-grain range.
A modern .54-caliber muzzleloader is almost universally manufactured with a 1-48 twist, although I have a still-serviceable 35-year-old side hammer gun in that caliber with a 1-turn-in-72 twist rate, which was good for patched round balls only. An 85- to 100-grain charge will effectively shoot .54-caliber sabots, conicals (try 425-grain bullets) and patched round balls with equal accuracy.
