Don't know what combination powder/shot measure you have, but on all of mine it is simply impossible for them to have total accuracy. Powder is marked in ¼ dram & shot in 1/8oz increments. All of them use the same setting for 2½ drams & 1oz. Simple mathamatics shows this to be 10 increments for the powder (2½ ÷ ¼) or 2.5 ÷ .25. The shot however being in 1/8oz increments has only 8 of them (1 ÷ 1/8). Obviously then the settings on these simple measures are a compromise, though adequate for most shotgun work. An older article from the American Rifleman which I have kept for many years stated industry standard for volume of Black Powder was based on .115 CuIn per Dram, thus a 5/8" dia measure 1 1/8" long has a capacity of .345 CuIn or Three Drams. The old Lyman #5 & #55 measures with drams & Grains markings for BP were I believe based upon this standard & were rather accurate for the powders of the day. I do not have any current stock of Goex, but last I had was still fairly close to those wt/volume combos.
