I usually just lurk here,and keep silent,but it's time to speak up!You are courting danger with 4198 in a snider.I use IMR 4759(thats a 9 not 6),26 grains under a 480 grain paper patched bullet with a filler works great in my snider carbine. I use dacron,use plenty,felt wads work also.
Due to the convoluted history of the 577 snider cartridge,you also need to fill the case with wads when using black powder,there is just to much room