big problem with those countersink bits is the drill bit is only like 1/2" long, making it USELESS for pre-drilling.
Contrary to this opinion, the drill bit should be
at least an inch long, probably more like an inch and a half long. Take the end with the little allen key nub and loosen the set screw that holds the drill bit in the countersink portion. Pull the drill bit out, making sure not to pull it out further than the set screw opening. Tighten the setscrew. Fire away. You may not be able to flip it around back into the holding mechanism (if yours is set up like that, that is), but that's the only downside to doing that.