Sometimes heavy bullets shoot high because of the added recoil.

It's not the trajectory of the bullet as much as the fact the recoil is elevating the muzzle before the bullet exits the barrel.

Most of the older sidelocks were designed for round ball ballistics, and a heavy conical would often necessitate a new (higher) front sight or some file work on the rear sight in my experience.
I can remember T/C's optional "primitive" (non-adjustable) accessory sights that usually required "drifting" the sight for windage and file work for elevation, but were great if you had a pet load you stuck with. Once sighted in they remained sighted in forever.