New York Times, August 5, 1878. Yes: cartridge placement would be key here. Standard operating procedure among ghouls was not to expose the whole coffin, just the top half. Then the lid would be prized up with a bar and/or hooks. The soil pressure on the lower part of the coffin helped lever the lid upward. Then the smallest dude in the crew would get down in the hole and run a rope under the armpits of the deceased, who could then be extracted with a quick heave-ho. The best of the trade took pains to restore the grave to an ostensibly undisturbed condition–leaving a mess was bad for repeat bidnis, see? Sometimes mourners would leave small tokens on the grave–a stick or a stone–as a quick way of determining if the site had been disturbed, but the ghouls knew about this trick too and did their best to anticipate it. Anyway, this torpedo gizmo apparently found a market and sometimes worked, judging from this prior post.
P.S. To those who like this sort of thing, may I recommend this excellent book.