A gunsmith in Kirbyville Texas used to use modern 12 guage blanks and build nice percussion single shot guns out of them. He also would take a barrel off of a modern single shot shotgun, trim off the breech ahead of the ejector, and run a 78ths x 14 tap into it, then make a breech plug out of a 3-bar bolt by running it in the breech threads to depth, marking it for length and top center, taking it out and cutting it off about 1/2 inch longer than the length mark, squareing up the rear part and welding on a tang piece. Built the gun and by using a modern barrel and a strong bolt breech plug, was able to churn up 10 guage loads. Fitted to a blank stock and using any old percussion lock, and making most if not all the furniture, it made a beautiful cheap, English style percussion gun from hell. Smaller bore guns can be made the same way. If you can, build it yourself, and when it's fitted, get a master welder to tig weld the plug for you.(not too much heat).also, you can braze a new under lug onto the barrel with no problems. The steel in the barrel is soft and will not harden, I'm told. I've fired several such guns but of course you're on your own. Good shooting, George.