It is either a black powder or black powder sub - it all measures by volume very well. Even with BH which is a smokeless powder - it still meters as a BP sub. In most cases other than Swiss, T7, and BH it will take a 10 gr. difference by volume to make a noticeable difference. Swiss, T7, and BH you might find a measurable difference @ 5 grs. by volume. For hunting accuracy you would never see the difference.
Now if you are hung up on supreme accuracy like you are shooting paper for a living - then by all means consistency is the best way to go - weigh it. But even then in the hunting application there are way to many variables to worry about a 1/2"
A few years back I did weigh everything - but today it is all volume for myself. But then again now today I am not trying to impress anyone with targets just harvest and animal of my choice @ 10 yards to 200 yards.