You determined which one was "right" for your powder when you weighed the charges from each measure. But to say which one is right for every powder is hard to say. Each brand of powder has a different density and each granulation will have a different density. 3f will weigh more than an equal volume of 2f. If you were to compare, say, 3f powder from different manufacturers, each one would weigh just a bit more or less than an equal volume of the other. So, I have no idea what each manufacturer of measures uses as their standard powder to calibrate their measure. What all of this means is that when you see a powder measure that is marked with a powder weight, you must add the words "somewhere around this amount" because you have no idea how the manufacturer calibrated his measure. However, in the end, it is not the absolute weight of powder that you put in your gun but the consistency with which you measure it. If you find that one measure gives you the best accuracy, use it and only it to measure the powder for that gun. In actual weight, it may be off a bit but that is not important, what is important is consistency. When you fill your measure, do not tap on it, just fill it to the top and pour the measure of powder in your bore. If you tap on the measure to settle the powder, it is hard to tap it exactly the same every time and that will result in a different amount of powder being loaded from shot to shot. When it comes to shooting a muzzleloading rifle, consistency in all things is the answer to getting the maximum accuracy your rifle is capable of delivering.