I'll list another source; Coonies in New Mexico.(No web site but listed by GOEX) I buy from Coonies as I save a bit on shipping. (West Coast)
Pyrodex is fine in certain applications, cannons ain't one of those applications. Dan Pawlak sent me some Pyrodex in the early 70's for testing (Dan was killed in '77 when the Pyrodex plant exploded). Pyrodex was/is a BP replacement under certain conditions. Pyrodex works great in percussion rifles when loaded properly. It was NEVER designed to work in flintlocks, matchlocks, cannons or anything of similar ilk.
Pyrodex requires a High Explosive to properly initiate it. In short, Pyrodex when ignited by flame in a cannon, can blow you to Hell. I guess I can sort of compare Pyrodex to TNT and this is a bad comparison I admit. Both can go off High Order or Low Order and you can't control it without a high explosive booster (or at least some type of booster). I have exagerated to some extent but only to make a point.
Good old gunpowder, the black stuff, is really forgiving when it comes to the Wide World of Explosives. BP is one of the most safe explosives I have ever worked with.
Get off the soap box.
And please, please, please, if you have questions about explosives, PM or e-mail me.
Bill