Nope, that's it. The reamer will follow the hole you made concentric with the boring tool, and with that short case your pilot will be in the bore pretty quick...probably before the shoulder of your reamer even starts cutting. When I pre-bore, I usually have a piece of new brass handy to check that I'm not going too large on the hole. I just bore straight in with a slow feed to true up the drill hole (after re-indicating on the throat of course). The pilot is in the bore pretty quick, so you have two support areas to keep that reamer tracking true (pilot and the shoulder of the reamer). Works for me although I know others bore out a taper to match the case.
