How do I create a real gun in MCreator?

I want to make a real gun in Minecraft (1.15.2). Like the ones in Flans mod and MrCrayfish's Gun Mod. But the one I made with a tutorial works very much like a bow, just reskinned. It is cool to start out with, but I ultimately want to make the real deal in my mod. So, I was hoping if anyone could give me some advice or point me to some tutorials. I will keep looking online until then.