bigdog - a true 2 bore muzzleloader has a BORE diameter of 1.325" - the rifling depth will increase measurement to about 1.380" if it has .025" depth of rifling. It should shoot a round ball of approximately 1.310" to 1.315" diameter in a heavy patch.

A true 2 bore ctg. gun will have a 1.325" groove diameter and shoot full sized 2 bore bullets of 1.325" to 1.327".