I have shot that load out of the NEF Huntsman, It is almost identical to another favorite load 85 grains volume 777 FFG with the 300 grain SST. I prefer the 777 FFFG for my conicals, and the 777 FFG for the saboted bullets.
If you were weigh out 80 grains Volume 777 FFFG and 85 grains Volume 777 FFG, you would be very close to the same amount of powder by WEIGHT. Both of the above loads are very close to the equivelancy of 100 grains volume Black Powder or Pyrodex.