Black powder historically has always been measured by volume. This negates the variable of moisture in the powder because of ambient humidity, resulting in more consistant velocity. Weighing charges is a total waste of time. If it makes one feel good, do it. Certainly not needed.
BTW, Switlik's chart is a joke. Under 1" he is showing charges that look more like musket loads. 60 grains was standard .58 cal Civil war minieball load.So I guess if your cannon has walls that thin, stick to those.
Leave the insults out of your posts they are not needed. You can disagree with Switlik's chart, but please if you can give us another credible source with a credible references showing charges for model cannon do so. The Dixie chart is very conservative and should be fine.
For shooting hand held and shoulder fired weapon you can get away with much heavier charges. Model cannons are not held in place; they are free moving shooting devices.
You can indeed load most model cannons far heavier than shown on Switlik's chart, but to what end. You will only make more smoke and noise, turn your cannon into a secondary projectile and tear your equipment up. Your cannon will not shoot better with heavier loads.
FWIW the safe recommend loads from N-SSA and AAA are not full service loads either and are substantially less than those loads.
Please join us in the cannon postal shoot and demonstrate that your heavier loads work better.
Volumetric measuring devices are used for measuring both smokeless and blackpowder. The procedure for smokeless powder is to calibrate the measure first by weighing charges and adjusting the the measure to throw the correct weight.
The practice with black powder is to set the scale on adjustable measure and start throwing charges. Or, just use a fixed measure such as the Lee scoops or other similar brass measures of a design historically used. No one ever bothers to calibrate these measures. Different brands and grades of powder have different weights in equal volume. In small charges you won't see the variables that easily. Go to the larger charges and the variables show up real quick. You need to calibrate the volume measure for the type of powder you are using. That doesn't mean you have weigh every charge, but it helps to know what charge the measure actually throws. The instructions that use to come with the Lee scoops had just such instructions.
The shape of the volume measure also affects it accuracy, There is a reason volume measures are long tubes versus a flat device like spoon. The small top surface area in a tube allows for better uniformity in filling the volume than a wide flat device and less variation in volume. Save the teaspoons for making cookies.
For my Pop can mortar I use a cut down 50 BMG cartridge case for a volume of 250 grns of FG. When I built this measure I learned that it would throw charges from 2-3 grains light to 2-3 grains heavy from one charge to the next. Good enough for smoke and fire, not good enough for shooting at Fort Pallet.. I found from my testing that a 5 grains increase over 250 grains meant an increase in 10 yards of range at 100 yards. That is a miss on the target. So for the large charges I weigh each load.
For my little 50 cal cannon I shot 45 grains of Fg. I have one measure that has a mark for 45 grains on it. That measure will throw a charge of GOEX Fg that weighs 45 grains. The cannon likes that grade and charge. When I load for that cannon I just set the measure to 45 grains, throw a few charges on the scale to verify it is throwing the right weight and then start throwing charges once iit is set, then check periodically.
This summer I am going to test some different loads. I willvolumetric load and I will verify the settings by weighing every time I change something and I will verify after each test.
I will say this again, if you have more credible safety standards than what we recommend here, please share them. We are listiening. If you wish to exceed or ignore these safety standards that choice is yours. Only you will have to justify ignoring them if you have an accident.
