I have always been told the in the realm of black powders, schutzen does have a slower burn rate. Swiss tending to be one of the faster, then goex, then schutzen. For instance, in my .54 common rifle, what 62 grains of 3 fg Goex does, it takes 70 of schutzen 3fg. I was also told this by one of their sales reps. Being slow does not make it a bad or inaccurate powder, it is just a characteristic. I also believe that it is good in many respects. I have also found that it does not leave a pressure ring of crud in the barrel ahead of the breech like many other fast burning powders.
Just some thoughts.