Re gms vs ml. you are correct in that liquids would normally be expressed as volumes. Unfortunately due to the rudimentary equipment available I could not measure volumes accurately enough to ensure repeatability. I did have a scale that would go to 1/10th gm so this appeared to offer the best practical approach. I believe volumes were weight adjusted based on density.

Hugh Lomas,
H.G.Lomas Gunmakers Inc.
920 876 3745