so, the grand kids have been shooting .22's for a while now. but i would like to kick them into the center fire category. i have a Marlin 336, that i bought the "youth" plastic stock set for. i plan on using cast 100g lee rn boolits ( https://leeprecision.com/mold-dc-311-100-2r.html ). and i want to start real low, and gradually bring them up from there. i have several pistol powders i could use, but i can't help thinking about trail boss. is it possible to download trail boss using filler (Dacron poly fill) to take up the space. i WILL be testing them out before letting the youngsters shoot them, just for safety sake. if not, i will just go with the pistol powders i have. my plan is to nudge them up over the next 2 years, to be able to hunt in the youth hunt our state has.