Under the GCA '68, blackpowder guns are not "firearms". Thus they are exempt from the marking requirements of modern firearms. Years ago, you could make them in shop class in High School. A lot of the old Spanish Jukar guns came in around the time of the bicentennial and still survive.
Literally anyone can make them in the garage or basement and not need to mark them.
Black powder operates at low pressures. Thus most guns of modern steel do not explode. Many older guns, having survived this long, are also unlikely to explode.
The Indian guns I am familiar with started life as flintlocks, sold without the touch hole drilled, so as not to be a gun in India and some places in Europe. Then of course some people drill out the touch hole.
They can, and hqve historically, made good guns in India. But if I were to get one, I would want to personally make sure the maker knew I intended to shoot it.
Dixie Gun Works and Cabelas have many blackpowder guns available.
Any non rusted out black powder pistol used to fetch 100 to 150.