I'd never doubt Rob's word on anything but... I had/have a POS T/C that was a flinter in plastic stock and advertised to shoot pryodex pellets...
I did shoot it and it did go off, but my, oh my...
I never thought to use loose pyrodex or subs in the tube and real in the pan...
Oh, it went off, but I swear even from the bench you could touch it off, bend over and retie your boot lace, then sit up and take hold of the gun afore it ignited...weren't much good for offhand with it's rather shorter bbl...
it shot quick with real BP till I took it afield...either the after Christmas season was so cold the cone shaped removable breech plug got chilled or the main charge would rotate behind the cone (tepee shaped breech) and I had two flash no booms and that did it for me... after too pffts and no boom on deer (those ops weren't that plentiful in my home area) I just gave up flintlocks and that gun just sits...
It's only saving grace was/is a removable breech plug like some in-lines... but I gave up entirely till Rob got me back into flints with a GPR....now moving to NE TN and I developed a bad gimp, coupled with no land access here, I Likely will be relegated to paper punching...