A gentleman on a discussion group I visited recently assured one and all that the Confederacy would never, nevah! use explosive bullets. Actually they did, on at least on one occasion.
The Jacob’s rifle, mentioned previously, was capable of firing a bullet with an insert of fulminate of mercury, which would explode on impact up to its maximum range of 1400 yards. Intended to be fired at artillery cassions, Jacob “believed it would revolutionize the art of war. Two good riflermen so armed could annihilate the best battery of field artillery in 10 minutes.” The bullet (which, unlike the standard Jacob’s bullet, had a hollow base) and insert are shown below (photos by Bill Adams)
The explosive tubes came in a tin, suitably packed to protect them from shock.
While the Confederacy did field a few of Jacob’s rifles (Captain Farley of Stuart’s cavalry used one — it’s not clear whether it was his personal weapon or not), and bullets from them have been recovered, they were few.
However, John Esten Cooke, an ordnance officer himself, describes one instance of a certain Captain Darnell using one with “explosive balls” at Cold Harbor. “I had been looking for a caisson to blow up. I could not get a shot at one, and I determined to use it like an ordinary rifle.” Darnell claimed to have fired 80 rounds, and there is no word on their effect on those unfortunate enough to be targeted. So far no fired explosive rounds have been found, which is not surprising.
As for the legality of the matter, in the 1860s there was no explicit prohibition on the use of explosive bullets, and as far as I am aware the Jacob’s was the only rifle capable of firing them.