There goes my theory. I thought T/Cs may have had a wider flame channel to allow larger grain powders to flow to the flash hole. Since BP ignites so much easier than any of the substitutes, I threw 5gr of 4F down the bore to make sure I didn't have a hang fire.
The only reason I used Pyrodex was it was supposed to have more velocity with less pressure. That meant the Pyrodex burned more slowly than BP, so most of the burn didn't take place in one location. It burned its way down the barrel. It's the same reasoning one uses a larger grain in a rifle. It will burn slower. I was surprised to learn on this forum, many if not most, of the competitive shooters shooting a .45 use Swiss 1.5Fg, whereas most people use 3Fg.