With an existing forearm I simply grab a piece of rod that fits snug in the forearm escutcheon screw hole, then turn a sharp point on it to make a center punch. Put the forearm on the barrel that's fitted to the action and then give my homemade punch a sharp tap.
Remove forearm and clamp the barrel in my machinist's vise and dial it in until a tiny drill bit sits in the punch mark and drill the hole. Then follow up with the correct size bit for my tap.

On new forearms for existing holes I made up screws with points I finger thread into the barrel's existing hole until just the point sticks out. Then I slide the forearm in place and give it a tap with my small rubber hammer. Remove the forearm and clamp in the same vise leveled, then drill the hole. Turn it over and counterbore for the escutcheon.

John Taylor wrote on Aug 21^st, 2025 at 11:20am:


The HF set only goes to 3/32" so wont fit most forearm screw holes, even with the escutcheon removed. Good for larger work though.

John Taylor wrote on Aug 21^st, 2025 at 6:25pm:


Most I have are #8-40 or 8-48. And without removing the escutcheon the hole is even smaller.

There is a small screw in the Winchester model 12 at the rear of the action that is a #1-72. I had to make one about 20 years back. Used a magnifying glass while machining. Dropped the first one in the chip pan and started on the next. A friend was watching and ask why I didn't look for it. It would have been the smallest piece in the chip pan.