It is a shotgun barrel extension for when you want to take out the person right behind you.
It looks like the end of the wooden dowel is pretty heavily worn, so whatever it is the dowel/cap part must have been installed and removed quite a few times over its' life.
**There is significant wear at the end of the dowel. And the dowel does go all the way thru.
That's an interesting shape on the end of the cotter pin. It doesn't look like it would hold in place very tightly because the tip of the cotter pin is the same diameter as the rest of the pin. How easily does it pull out?
**It's a cotter pin that had a ramp of sorts (angle) filed away (so it wont back out) The pin needs to be spread out and that keeper feature would work again. Now it's loose.
Is the hole in the tubing wall smaller on one side to better allow the cotter pin tip to click and lock into place via a slight spring pressure?
Does the wooden dowel piece go all the way through the metal cap attached to it or is the cap piece all metal on the end?
Neat find. I am interested to know what it ends up being.