That's a cool find, though I don't think it's a projectile. IMO it'd be too big and awkwardly shaped to fire with any accuracy. My guess would be that it's some sort of handmade item from a bored soldier in camp... maybe a little sculpture from a pounded-out bullet or something. It reminds me a little bit of the tip of a scabbard; if someone poured melted lead into a bayonet scabbard tip the result might look something like this.