I just checked Cabelas, unless I’m blind I cannot see percussion caps anywhere on their website.Check Cabelas from time to time you can place an order there, may take two weeks to get the product but that worked for me to get 3 boxes.
If the hammer has the same kind of lousy steel as my Ruger Old Army...I would suggest not dry firing the pistol at all (unless you use percussion caps) --- If you do...wear eye protection --- Since I've broken two of my Old Army hammers while dry firing them, (with the thumb cocking piece of the hammer cracks and flies off directly at the shooter with speed).
That's why I think Ruger gave up on manufacturing the Ruger Old Army, even though the instruction book said it was okay to dry fire the pistol.
That makes for a pretty close tolerance which doesn't allow for much variation in the cap's metal thickness among different brands-- or how far down onto the nipple they fit due either to the amount of primer fill or how far/tight you push the cap down onto the nipple.I use to file my hammers so they cannot touch the nipples but just the caps. After that I use to harden it by the old heat and oil method. As simple as it sounds.