I have this project derringer that I've disassembled and cleaned. You can see how corroded it was from the pics. Now I'm trying to reassemble it. I had to order a trigger spring for it, but I'm not sure how to install it? The trigger doesn't seem to want to come forward enough to install the spring. The trigger appears to only be able to be installed one way. What am I doing wrong here? Anyone assemble one of these that can give me some guidance? Part number 13 in the schematic below. thanks!