Hi Dennis
I have only seen the drilling of a gun stock through hole once and it was done after the stock shape was initially cut from the blank. If the through hole is drilled at this point it provides the rotational Axis line for the stock blank in a duplicator.
The drilling method for the hole used a jig and a modified drill bit which had a smaller diameter extension rod welded to its base, the smaller rod diameter allowed for wood chip removal thus preventing the drill from jamming. The jig consisted of a close fitting to the drill metal tube some twelve inches long whose angle could be adjusted to give the correct path from the stock butt to head with the wood blank firmly clamped to stop any movement. The drill is passed through the tube into the wood and with frequent removal of the drill to remove the wood chips, also to further improve stability of the jig shims are fitted in the tube centring the drills extension rod keeping everything in a straight line.
