So far, it seems most of the guys are getting terrific results using 90 to 120 grains volumetric of the BH209 - and you will probably find a load in that same ballpark.

I would start with 85% by volume of any load with Pyrodex for what I believe would be similar velocities. In other words, if shooting 100 grains by volume of Pyro - drop that to a starting point of 85 grains by volume of BH209. I don't know that anyone has done direct comparisons to charges of loose Pyro - but I think my suggestion would be both safe and close to accurate.