perhaps:

Reference about Samuel Baker in the book.

"Mr. Baker has stated, that 4 1/2 drams will drive a ball of that size through both sides of an elephant's head, and with 4 1/2 or even 5 drams may be used in such a rifle without any very unpleasant recoil, and without any bad effect on the accuracy of the ball, but the reverse."

He went on to describe the slow rate of twist necessary for the round ball gun, unlike the current makers who are putting in too fast a twist.

Seems to me John Taylor used a .577/450 (480gr. at about 1,340fps) for a period in his poaching career due to losing his other "rifles" in a river.

That rifle the ultimate, no - did it work? I don't know, seems to have worked.