My two Lyman Flintlocks are powder pigs also. The Trade Rifle for some reason wants 90 grains of 2f and NOT 3f. When I tried 3f it sprayed all over the place. My Great Plains Hunter shoots sabots and I usually shoot 90 grains with them depending on the weight of the projectile.

For a first day on the range.. that is darn good shooting. Also try moving your pan powder around. My Trade Rifle likes it on the outside edge of the pan the the Great Plains likes it up near the touch hole. My T/C Flinter wants just a little powder on the outside edge. Its all learned with time. I would shoot that a little more before I start to file. But since you're at the top of the ramp already a little filing might not hurt.

That RMC vent liner is the only one I will use.