Derringeer, can I recommend a good read? "The Gun and Its Development," W.W. Greener, can be had in various versions (Kindle, paperback, leather-bound reprint) from $9.00-up. Besides details in historical attempts to build the better projectile-firing mousetrap, many B&W photos, sketches, and engravings show engineering details of things previously tried. The text explains well why many things did or didn't work or become popular. Reid Coffield & Larry Potterfield's "Building Your Gunsmithing Library" also serves well as a bibliography from which to start shopping for both historical and technical references.
Looking at your other posts on this forum, I remember my own enthusiasm about inventing or refining ideas for things to generally advance the art and science of shooting, or at least experiment to satisfy my own curiosity. I don't regret that the first thing I spent a lot of money on was books, nor that I spent more time reading than tinkering in the first few years. I found that many of my own "original" ideas actually duplicated earlier concepts, as well as why some of such designs (even those patented) should stay in the "Historical/Academic Reference Only" and "Kids, Don't Try This At Home" categories.