Systems for drilling or tunneling include an assembly for accelerating a projectile into a region of geologic material. An interaction between the projectile and the geologic material extends a borehole and forms debris. The debris may be reduced in size by moving the debris to a crushing device. The reduced-size debris is then moved toward the surface using fluid movement. Water jets or other types of devices may be used to cut or deform a perimeter of a region of geologic material before the projectile is accelerated to control the shape of the borehole and the manner in which debris is broken from the geologic material.