My suggetion is to make your powder measures of the smallest diameter tubing or smallest diameter holes drilled in antler you can get away with for a given calibre. The reason is the smaller the hole, the more even, throw to throw they will be. I was able to hold powder charges thrown with both 2f and 3F to within 1gr. weight,using a 3/8" diameter brass tube measure. Using a horn measure, with a 1/2" hole, the variations were way over 3gr., throw to throw.
This is largly calibre specific - ie: a 3/8" or larger hole in the measure makes it difficult to pour the powder into a .25 or .30 cal rifle barrel without a lot of spillage.
Too, a 5/16" tube holding 110gr. of 2f would be unbearably long to use for a .54's measure.
The standard measures having a 3/8" inside diameter throw much more accurate charges, throw to throw than a 1/2" hole will throw. Somewhere in the archives, is a thread dealing with this, along with a test I did using several or maybe only 2 different diameters of measures. It changed my outlook on measure diameters.
I suspect if you can thumb-start your patched ball, the diameter of the measure won't matter much at all, if you get my drift. With a black powder rifle, consistancy is a large part of accuracy. My most accurate rifles are the ones which give me less than 10fps per shot variation. Consistancy is something to strive for- if you are intersted in the accuracy part of this game.
All marked measrues are approximate - the numbers really don't mean anything in terms of accuracy. On top of granulation sizes, and pouring methods, both which change the actual weight thrown, different makes and even different lots of the same make of powder have different specific gravities - which absolutely gaurantees different weights with the same from the same measure. in other words, whtout a scale, you have no idea what your measrue is throwing. If it isn't important to you, it matters not.
If knowing what the measure throws is important - as in - you might want to make a period correct measure to throw that amount, or simple must know what it's throwing in case you lose those 'sticken' measures - you need to know to make another.
I use an ajustable to find the load that gives the best accuracy in a given gun - smooth or rifle. I then weigh that charge on an accurate scale and I record it.