I've been thinking about these pictures all day. I work at an old airfield and from time to time we find horseshoes, casings and random bits. Well, for a long time I had what looked just like one of these on my desk, but I didn't know what it was and got tired of the clutter and threw it away. Now I'm almost positive it was an old bullet, only mine was solid and had a flat bottom. It was also in near mint condition, a dull brown/gray color if I remember correctly.
I'm glad sites like this exist to spread knowledge that a random idiot like me is just ignorant of. It could actually save an artifact's life.