Yes i did have to open the flash hole in the very nice TOW nipple. Obviously the fire path in a musket is shorter than the Sharps so a little drilling and I get 100% ignition when using RWS caps. No nitrate just tracing paper (thanks Mike B.) and hair curler paper for the flat base. Also for the first couple of shots the nipple gets a bit of FFFFg to dry out the fire path. The breech block is cleaned by being soaked in Moose Milk so everything inside is clean and lightly oiled.Nitrating the paper is not needed. I have never nitrated my cartridges.
Always use the strongest caps you can get. I use 6-winged caps. Reliable and fast ignition. Sometimes, the flash hole needs to be opened up just so little.
Bunk