Muzzle Loaders Association of Great Britain (MLAGB) see http://www.mlagb.com/wedgnock.htm
I have shot musket, revolver, and rifle here as part of their BP aquaint. A Quad / Clay shoot could be combined.
A work colleague from Bristol has made this cannon, see http://www.artillerysociety.co.uk/
It would be really good to see how memebers best BP measures up to commercial powders, using any of the above implements. No doubt this would still be prohibited.
TTFN
Terry