There a few references to flintlocks in the stories. Presumably these are the earlier types and not the "true" flintlock of the 17th century. en.wikipedia.org/wiki/Flintlock The Moon of Skulls: "in an instant Kane's pistol was in its owner's hand. A second's investigation showed that it was still loaded and the flint still in place." The Hawk of Basti: "Kane's cold eyes roved among the trees; one lean iron hand hardened on the carved sharp - pointed stave he carried, the other hovered near one of the flintlock pistols he wore." The Footfalls Within: "Some carried in their wide girdles long, silver - chased pistols of more effective pattern - flintlocks of Moorish and Turkish make."
Solomon Kane is one of my favorite characters. He is , as George Clooney put it, a mean MotherF***ing Man Of God. And if you can't find the stories for free, Amazon has all of REHs stuff for real cheap. Like .99 cents for a collection.