I found an unusual piece of brass at the range the other day. In the pic below, the one of the left is a .300 BLK, the one in the middle is the mystery brass, and the one on the right is a .223 Rem.
The head stamp on the mystery brass says .223 Rem, so it's obviously been reformed. The overall length is 1.550" and the mouth appears the be .30 cal.
A longer version of the .300 BLK? Anyone know what this is?