well it depends what you have. because i use blender you i click F9 and click new for "Vertex Gourps". Click b(make sure your in edit mode) and select the vertex point where you want your bullet to come out. Then name it "Muzzle"(i think. correct me if im wrong.) and click assign. and your done :) . to make sure you did this correctly click deselect, then select, then deselect, then select, then deselect, then select, then deselect, then select, and so on. it should start blinking as your clicking. i do this for both fun and to review. your welcome.