In my knight disc rifle, my favorite bullets (250 grain barnes expanders) shoot 1" groups with 150 grains (pellets). These same bullets shoots about 21/2" groups with 100 grains. On the other hand, I have not been able to get 300 grain or heavier bullets to shoot as well with 150 grains. They seem to better with a lighter load. I guess the point is you have to experiment and find what your gun likes. Fortunately, the barnes expanders perform so well I have no reason to change unless I am elk hunting in which case I live the 2" to 3" groups the 300 grain expanders make with 150 grain load (elk are a big enough target that within muzzleloader ranges, that they are more than accurate enough). I think that absolute consistency in the cleanliness of the bore is critcal to tight groups. Without cleaning the barrel, the 1" groups open up to 2+". It might pay to take extra precautions to ensure your barrel is in the same condition for each shot. The only way I know to do this is to get the barrel completely clean--otherwise it is difficult to compare the condition.