Engelhardt gives the following black powder proofs on British for guns of class 4 (Double barrel breech loaders of smooth bore). 1868-1904, 16ga provisional proof = 10 3/4 drams of Tower Proof (TP) Black Powder. Definitive proof = 6 3/4 drams TP powder. Both used a round ball. Beginning 1875 if the gun was choke bore a weight of shot equal to the round ball of the widest part of the bore was used. No pressures are given.
1904 16 gauge Provisional = 10 3/4 Drams TP powder with 399 grain bullet. Definitive = 5˝ drams TP powder with 1 1/3 oz of shot. Service load = 2 3/4 dram powder with 1 oz shot.
Still no pressures given.
