By 1860, Forsyth,and others were experimenting with explosive 'shells' for shooting dangerous game, starting with General Jacob's designs and changing them for more rapid detonations.

These were called "Shells" and could very well be what Baker was referring to.

A 10dram (270gr.) charge is not a max load in a 4 bore and in a 2 bore, would be very mild load indeed. By mild, I am not saying it would not kick, rather I am referring to it being a 'light' load.

Forsyth spoke of loads used with these exploding "shells" and they were indeed 'lighter' than would be normally used. On top of that, the ranges would have to be very close due to trajectory.

Higher standard/normal velocities were not conducive to having the 'shell' explode at the correct time - the charge had to be adjusted for each animal sought, whether elephant, tiger or buffalo. For rapid or shallow penetration explosions, charges as light as 2 to 2 1/2 drams in an 8 bore. That's only 54 1/2gr. to 68gr. black powder a piddling charge in such a huge bore. I use 6 drams in my 14 bore rifle, for hunting moose. Yes, more than necessary to kill, but necessary to give a point blank range, to 130yards.(6" kill zone)