It was not the core but the weight of the drill rods and deviation. Stand a kilometer of pipe on its end and try and pick it up, hold it, break the threads, remove sections and still be able to move the drill around with a helicopter. We are not able to use the big deep drills that Sudbury uses. I admire what they did do with the conditions they had. It is those who don't do it that complain the loudest from their chair.