The exact core measurements would be very nice to know. Baker wrote
IN the March 23rd, 1861, Baker wrote that:

"I strongly vote against conical balls for dangerous game; they make too neat a wound, and are very apt to glance on striking a bone. The larger the surface struck the greater will be the benumbing effect of the blow. . . In giving an opinion against conical balls for dangerous game, I do so from practical proofs of their inferiority. I had at one time a two-groove single rifle, weighing 21 lbs., carrying a 3oz. belted ball, with a charge of 12 drachms powder. This was a kind of " devil stopper " and never failed in flooring a charging elephant, although, if not struck in the brain, he might recover his legs. I had a conical mould made for this rifle, the ball of which weighed 4 oz., but instead of rendering it more Invincible, it entirely destroyed its efficacy, and brought me into such scrapes that I at length gave up the conical ball as useless."

3oz. is 1,312gr. & was the weight of the belted ball - for a rifled gun. The actual bore, not the groove dia. would have been in the 5-bore range, .977", or so, as needed to give room for the necessary patch.