I might get some grief for this, but when we say 40 gr by VOLUME, we are saying 40 gr by VOLUME of REAL BLACK POWDER.
Numerous writers and authorities have taken REAL BP, GOEX, today, and weighed 100 gr and all 4 grades are within 2 grains, even 4F.
IF you have a scale, set it to your charge, fill it, and weigh it, if you don't have one, see if one of your smokeless shooting friends has one, and weigh it at his bench. Set your measure for a higher charge and pour it in, and raise the thimble till it is flush. Check to see what it reads.
I bought a Traditions measure, filled a 38 case, supposed to be 24 gr BP, weighed it, it was 24.3 gr, filled the measure set at 20 gr, and it was over 1/16 low.
Now, at 5/8 inch deep, that measure would be throwing charges of at least 30 grs when set to 20 grs. 50 % high. Difference would be lower at higher charge setting because the thimble in the center of it is smaller in diameter than the brass tube enclosing it.
BP weighs 100 grs per 100 grs volume, or as near as dammit. You WEIGH BP to get BP equivalent by VOLUME. The other powders you go strictly by VOLUME equivalent, unless you know the specific gravity of them.
Them of you who cannot get a ball to seat on a given VOLUME charge may be way overloading your pistol.
Can't anybody believe that just because they scribe some marks on a thimble, or mold them in to it, that they might just not be accurate?
Weigh your BP, or if you use strictly subs, go to the site, find out what the equivalent weight is, and set your measure to that.
BP weighs 100 grains per 100 grains VOLUME, the upper limit is 2 grains over, and that could be a leveling error, no matter what the fineness of the powder. Too many "experts" have said that for you guys to disagree.
RK, if you were loading 2F insted of 3F, samey same, would still be the same rammed pic. The volume is the same.