If your smith follows the print above there shouldn't be a problem at all. The M40A5 is Item #3 on the list. It should go without saying but all turning needs to be done in one set up to make sure the threads are running with the .775" diameter.
Anyone who uses one of his base set is going to run into the same problem. His rear lug is left oversize intentionally with the though of filling it to match the clip slot on your action. But if you have Virgin action you can cut the action to fit the base which is much easier. The very first...
One last note on the M40 drawing above. If you want that thump notch with the "S" notch see my dimensions above but instead of the .236" "Y" Dimension use .200" and then use a dremal tool to hand sand the point to create the "S" version. It's not hard but you should take your time. Good Luck.
I will say the M40 drawing two posts above were how Remington did them on early, early, early in the M40 line up and the arrow on the thumb cut that is missing is also .33 R but location is anyone's guess. Once the rifles started being build by Quantico that thumb grove was no longer done due to...
Let's keep this one alive. If anyone has a specific question on clip slotting I will do my best to answer, I don't know everything but I'll share what I do know.
Actually the A3/A5 is cut with the action laying on it's side with the base holes against the mill vise jaw and you plunge with 3/4" diameter carbide endmill. This is just for the thumb notch. Man wonder how many hits I would get on Youtube showing how to Clipslot a M40A3/5? lol