"The second test, made when the gun is ready for delivery, is carried out with double powder charge and double shot load."
Banc D'Epreuves Des Armes a Feu De Liege, 1906
Third Obligatory Proof for double breech loading sporting weapons; finished barrels attached to finished action
12g / 18.4 mm with 11.6 gram = 179 gr. = 6.5 Drams powder and 47.3 gram = 1.67 oz. shot
Hunter Arms' definitive proof for 12g 2 3/4” was 6.5 Drams with 1.687 oz. shot = 14,200 psi + 10-14%
Ithaca advertisements stated that barrels were proved with a “double charge of powder and 1 1/2 times the normal shot load”; or (possibly) 6 1/2 Drams Black Powder with 2 1/4 oz. of shot if the standard load was 1 1/8 oz. shot and 3 1/4 Dram Eq.
