The stock pistol as sold by CVA did not have a musket cap nipple; I presume it was modified later? Or perhaps the OP meant magnum caps.
Magnum caps should ignite the Pyrodex pellets; if not, use a small charge (2-3 gr) of loose powder before you load the pellet.
Simon is correct; 30 gr is within the capability of that barrel. I would think 40 gr is the limit it can burn effectively.