Congrats on your new Walker!
Yup, you should invest in a volumetric measure if you plan to shoot BP or BP substitutes. You may weigh real BP if you wish. Theoretically, the weight and volume measurement of real BP is the same. However, in the real world it will be slightly different but not different enough to make a difference...if you know what I mean.
BP substitutes such as Pyrodex and 777 MUST always be measured by volume
. As previously pointed out, Pyrodex is one-to-one on par with BP when measured by volume. 777 loads should always be reduced by 15% in order to give you a close approximation of the equivalent BP or Pyrodex load since 777 is more powerful than real BP.
Get yourself a volumetric powder measure such as the Thompson Center U-view measure.