Help me ID this mystery case.

[desertrat1979]

So I found a piece of brass at the range that has me scratching my head. Its got the excact came dimentions as a .223 Rem, except the length. I measured it at 1.545" and the headstamp says 270 and 82. I am sure the 82 is the year, but the 270 is screwing me up. What is this cartridge?

 

[leadbullet]

222 rem magnum?? a pic of it next to a 223 case would help a lot.