The first thing i would do is free float the barrel, and see if that cure your issue. If free floating doesn't keep the first shot within 2" of the succeeding shots i would purchase a
new $360 rifle. Then i would purchase the
shim kit, and make the primer of your choice snug, or slightly compressed in the socket when the rifle is in battery. If you shoot Blackhorn powder, you will also want to either modify the breech plug, or purchase a
Blackhorn plug.
My bet is this package will kill elk this next season, and the next, and the next.......... out 150 yard. My bet is this rifle won't put the first shot 18" high. Me, i am so sure the first shot won't be 18" high, i am betting $100 it won't.
Me, i have never shot this rifle nor did i stay in a motel last night, but i have shot an Optima several times.