Odd caliber found

[Yellowfin]

While sweeping the range for valuable brass today I found a particularly curious case on the ground I've never seen before and it struck my curiosity. It's very short and small caliber but I couldn't tell if it came from a rifle or pistol, foreign or domestic and just really super exotic. The headstamp gives its dimensions: 5.7x28mm. It looks like a .17HMR trying to grow into a .223. I am totally puzzled. What is this? What shoots it? Intended purpose? Availability?

 

[Scorch]

It's a round for the FN FiveseveN pistol. I believe they also make a carbine for the round. High velocity round designed for police use, but it has been available to the masses for a while.

 

[Steven Mace]

Yellowfin, for some basic reference information on the 5.7x28mm cartridge you can visit the link below. It was created by FN and is chambered in their Five-seveN pistol and P90 carbine.

http://en.wikipedia.org/wiki/5.7_x_28_mm

Hope this helps!

Steve Mace