I was digging in a box today and came across a tiny glass jar with a bullet in it. The jar has "1866" written in small letters on the label in ink. This bullet is obviously a rimfire, and measures 0.406 by my caliper. Somebody gave it to me many years ago and I just unearthed it today while looking for a sizing die that I had misplaced. Wouldn't it be a black powder bullet if it actually was from 1866? I think it would be neat.
It couldn't hold more than 10-15 grains of powder in there though? I have no clue what the headstamp (the letter "M") means. There is not any other writing on the jar.
Here is a pic. (Link to more pics is below)
And here is a link to more pics of the same bullet.