Just curious if this could be possible canister shot. Found 12 inches deep, 1940s era house. Is 1/2 inch in diameter. Curious if anyone has any ideas. Thanks in advance.
You'll need a good diameter of it is what I've read here many times for anyone to attempt any positive identification of what you may have here. Outside of that it's all guess work.
Way too small for grape or canister. Ball bearing. These things are common finds, many kids used to play marbles with ball bearings, we called them "steelies" back in the day. Also used widely for slingshot ammo and still sold as such today.
Gunsil is correct... it is too small to be a Canister-ammo ball or grapsehot ball. Besides the fact that there were no iron 1/2-inch canister balls (nor grapeshot balls), your measurement of 1/2-inch seems to include the thick rust-crust still on the ball, so its actual metal diameter is less than 1/2-inch. Sorry to have to give a disappointing report, but it is a ball-bearing.