I can't remember the names of all the shots but strictly speaking about the procs, assuming all of these proc, 1, 2, 1, 3, 2, 1, 3, 2, 1, yada. The goal is because of the cast time with barrel being a thing, you don't want to wait to see if your procs happened. So instead, you go ahead and start your next proc rotation. So when you cast your first skill, it should be with quick reload or reload so you KNOW your second skill procs. Then use your second to proc third. While you wait to see if three proced, cast first again, it will proc second. At this point you should have 3 and 2 ready to go. Use 3, then use 2 and hope three procs again. If it doesn't, you start from the beginning. From there you just add in all your other skills using the rotation shown in Miru's link.