Hi Graham
Good point you have bought up, I don't really know. The cut outs of the stock at the end are really what you want to probe, they are the hardest bits of the stock to machine. All stocks are different in the front actions from maker to maker,I assume you would get over that problem by either using a dowel piece from the bolt that holds the stock onto the action to a live centre that will trigger the probe to stop but still give you the majority of the internal cut outs and design, or you would have something written in the macro to say don't probe lower than the centre line of the rotary axis.
These are only my thoughts that's why I'm asking for help on how to do it.
Katoh