Different powder measures will throw slightly different weights, and how you fill and handle the measure will affect the weight of the load.

With my adjustable brass powder measureset at 100 grains and using Pyrodex RS, if Ifill it to overflowing - then tap the side of the measure fivetimes with a pencil to settle the powder (it settles about 3/8") - then fill it to overflowing again - then tap it once - then level it off - and weigh it, I get 78 grains weight (average of 5 measured loads).