I decided to share the following photo knowing that I am opening myself to some criticism for not forging the spring. If you don't need to be absolutely historically correct, this is a quick and easy way to make a spring.
The photo shows a slightly updated implementation of a very old patchbox release mechanism. The part that is new to me is the design of the release spring I used. I cut the L shaped spring out of 1/32" 1085 with aviation snips. It was quick and easy. I just had to drill two holes for the slot and cut out the waste between with a jeweler's saw. Then I drilled and countersunk the hole for the screw. Next to last, I bent over the little tab at a 90 degree angle. The final step was to heat the tip and bend it over with some needle nose pliers to form the hook to engage the catch. I did reduce the the amount of hook on the belt sander.
Inletting was done with a 1/4" chisel and a 1/16" morticing chisel. I had to just cut a slot a little wider than the spring is thick and inlet the roughly square tab. The tab inletting and a nice tight screw keeps the spring in place.
You might ask what I was doing before. Well I was making a V shaped spring that had one leg tightly inlet into the butt stock. It was always hard to inlet. The other method was to forge out a spring with a similar 90 degree tab that I could screw to the butt piece. Getting that positioned correctly is a bit tricky. Putting the spring in the right place with it attached to the buttstock is easier.
The pushrod was forged out of 5/16" mild steel rod. I decided to hold it in place with a pin because it keeps the pushrod from getting wedged into the butt piece.
Anyway, here is what I did; a modern update to an old design.