I was shooting Triple Seven 2f yesterday in a LK-II which is a plunger style, with Winchester Magnum #11 caps and had not ignition problems until something strange occurred which I have yet to figure out. Today I took the same rifle out, same powder, same every thing and shot 10 rounds without a flaw...

Pyrodex RS is easier to ignite of the two mentioned. But if you prepare the rifle correctly, either should work just fine.