A system and method for boring a hole in rock with a digger derrick; which utilizes a hollow stem auger, a kelly bar, and a core barrel with a top support member with a hole therein for receiving the kelly bar with a detachable central pilot bit thereon which is translatable up and down with respect to the core barrel as the kelly bar and auger are manipulated. The kelly bar is selectively positionable with respect to the auger so as to allow the ability to retract the pilot bit inward into the core barrel and to shorten the separation between the pilot bit and the auger.