I obtained a bunch of blackhorn 209 charge tubes for free. They are marked for "charge volume" in grains from 20-120 grains by volume. Im not going to use blackhorn 209. So if i fill the tube up to the 60 grain marking with FFG Goex, or Goex OE. Will that in fact be 60 grains of Goex? In otherwords does FFG and Blackhorn 209 measure the same in volume?