The case label with a c. 1880 William Sumners, Liverpool 12b specified Curtis & Harvey No. 5 Black Powder:
Light - 2 3/4 Dram with 1 oz. shot (1180 fps)
Medium - 3 Dram with 1 1/8 oz. shot (1200 fps)
Heavy - 3 1/4 Dram with 1 1/4 oz/ shot (1220 fps)
Lord Walsingham
On August 30, 1888 when I killed 1,070 grouse to my own gun in the day, I shot with four breechloaders. No.1, a gun made in 1866 by Purdey, subsequently converted from pin-fire to central principle, to which new barrels were made last year. Nos.2 and 3, a pair of central fire breechloaders, made also by Purdey, about 1870, for which I have likewise had new barrels. No.4, a new gun made by Purdey this year to match the two mentioned above, but with Whitworth steel instead of Damascus barrels. The guns are all 12 bore, with cylinder 30 in. barrels, not choked.
My cartridges were loaded by Johnson, of Swaffham; those used in the down-wind drives containing 3 1/8 drs. Halls Field B powder to 1 1/8ozs. No. 5 Derby shot; those used in the up-wind drives (where the birds, of course, came slower) had 3 drs. only of the same powder, with the same shot; not hardened shot in either case.
1896 Lancaster
E.C. No. 1 42 grains = 3 Dram with 1 1/8 oz. shot
A 1906 Holland & Holland hang tag specified the gun was regulated for 42 grains Schultze = 3 Dram with 1 1/16 oz. shot.
The standard 2 1/2 12g British load according to the 1907 edition of Greener's The Gun was 1 1/8 oz. 3 1/4 dram (1255 fps).
BTW: UK 6 = .10" = US 7; UK 5 = US 6
