...I am going to build another one from junk.
Some time ago, I came up with a spare breachblock for a trapdoor at a real good price. So I figured, why not buy the rest of the parts and then I'll have two.
So I am starting with a barrel which I bought off of ebay for 55.00. The ad listing said the barrel was badly pitted but I think it cleaned up okay. This is a standard length barrel with the rod bayonet fitting.
So I started out with a hack saw