the greyhawk is basically a stainless new englander. 1/4-28 theads. you can use #11 nipples or the musket nipples in that thread size. i like the musket nipple better because musket caps are easier to pick up. i love the rws-caps but cci-s will do. patch round balls will do you good. thompson center maxi balls in 370 grain will shoot shoot well too if you really wanna anchor the deer. sabots are a toss up . you might get lucky. id start at 70 grains of pyrodex rs and work up to 80 grains if need be.