Just got a slightly used Knight muzzleloader. Took it to the range to sight it in and started off at 25 yards. shot five rounds and all were 1/2" low at the bullseye. At 50 yards shot ten rounds and left a nice grouping but it was 6" low and scope adjustment would not correct. Shooting 100 grains of pyrodex rs with 250gr Tc's with the yellow sabots. Started with 90 grains and moved to 100 to see if it changed the pattern. Still shot low. any suggestions?