Oh I see. So it sounds like after drilling the hole, you would rip it lengthwise, slicing the hole hole that is open to the top that a pipe (barrel) mounts in.
One blog that I scanned used a ball end router bit on a router table instead of trying to drill a deep hole in the end. This eliminates the need to drill deep. Of course you would use a straight bit to hog out as much as possible before running the ball end bit into it from the end.
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.