Concept of a 4 shots Derringer-like pistol, double action mechanism. I took the ''4 bangers'' concept but I modify the internal cam entirely (non-return grooves, variable radius for one way rotation and direct linear striking + indexing pin at the top). For now, only ignite black powder primers, not modern ones. Not what I want but I publish it anyway if you want to improve it. I will work on another related design. The zip contains stl and step files.