What is this?

[ray1970]

It appears to be a .22 rim fire round of some sort. The case is approximately 1/4" long, the projectile is very pointed, and there is what appears to be an acorn on the bottom of the cartridge.

http://emob102.photobucket.com/albums/m98/rjs1970/photo_zps86acb077.jpg?t=1378902184

[kidicarus13]

It's called a .22 CB Short. I think CCI along with other mfg make them. Good for shooting sqirrels, birds, etc at close distances... say "in city limits"

[sandman76]

Might be one of the primer only type. Kind of like shooting a pellet gun. Aguila Colibri. Supposed to only be used in a handgun but I've shot them in my basement in a Marlin single shot with a trap. Nope case is too short to be that type

[spleify]

Got anymore, different/better pics

[Rabid]

Could be a 6mm rimfire
Edit: pretty sure it is a 6mm cb made by RWS
Edit 2: or a 4mm cb

[TFOGGER]

I used to get these all the time for pest control when I was much younger. They work well in revolvers and single shots, but won't feed in anything that uses a tubular magazine. Ballistically, they fall about 30% short of a 22 short, but pack plenty of walllop for squirrels, pigeons, and rats.