First, percussion caps, or primers, for firearm ammunition or black powder firearms are the most dangerous part of the entire operation. All primers or percussion caps are made from primary high explosives, the most sensitive type of explosive known. These usually require fairly exotic chemicals and are tricky to make properly--i.e., without blowing your fingers off. If this topic proceeds any further, it's simply going to degenerate into ways to make primary high explosives, and for that reason, I'm locking the topic. My advice: get a commercial percussion cap that works for you, or redesign your gun. It would take some very dangerous experimenting by someone who is very experienced with explosives to make proper caps. I would certainly just buy them myself.