And I have to believe it is because of my workmanship. It's my first caplock build, my flinters run like tops. But I've never had a caplock that ran like I wanted. I think it's because I don't know what they are supposed to be like, geometrically.
Symptoms: Pop a cap, I get nothing at the muzzle. Load and fire, cap does not ignite main charge. Load a charge, the powder does not funnel from the main barrel into the nipple barrel. open the cleaning screw and charge the nipple barrel with some 4F and the thing fires great.
I have the nipple barrel threaded into the back of the barrel so that spark should hit the main charge when loaded. Diameter is I believe 1/4 (28 pitch threads). straight shot through, nipple barrel is cut so it does not protrude into the main barrel. Nipple is unmodified from as purchased, has a very narrow channel from primer to the barrel.
I have a cheap borescope, here's the best I could do:
(I think the only one that is hard to see is the one of the nipple barrel transitioning into the main barrel. I'm just trying to show the main barrel wall is flush, that nipple barrel piece does not protrude)