Hi, I got this projectile in a carrier bag full of odd fired cases and projectiles (all identified, nothing rare). It is made of lead, and has a line where it was cast. It is 21.3mm (0.83") long, and has a diameter of 11.42mm (0.45" Exactly). It has 3 deep slanted grooves running along the body (the last one of these has traces of a dark greenish, wax-like lubricant). The base has a steep, cone-shaped indent 7.2mm (0.29") deep. Is this a projectile intended for a cartridge, or a muzzle-loaded projectile? See picture below: (Sorry about the dark photo).
Falcon, please review the photo posting FAQ. Toward the bottom, you’ll see a section about size and photo editing software. I edited this one for you. Unfortunately the original was somewhat fuzzy, likely because of the lighting when it was taken, but this should still help: