No it is not required to weigh BlackHorn 209. Use a volume measure and have fun. The reason a lot of people weigh the charges is they carry pre-made charges. And some of these people are trying to squeeze every ounce of accuracy out of their rifles. Heck some of these guys on here will shoot 200 yards or more with their muzzleloaders. I commend them kind of for being so diligent to take the extra effort to get the best possible accuracy from their guns. When they weigh the charge, that's just one factor out of the equation.

I have weighed charges. But I find I can throw charges out of a measure and get excellent accuracy with any powder. Although when I weighed charges I did shoot a little better group most the time.