My dad always picks up interesting and unusual brass he finds lying around when we shoot near my parents' cabin. I was looking through some of it this weekend and came across this... Judging by the LC headstamp and the fact that all the diameters match 5.56 brass, I'm guessing this is what it's based on. The case mouth is sized right for a .30cal bullet. Anyone have any idea what cartridge this is? Also, I like how tall our backstop is when we shoot. I don't have to worry about Laurel accidentally shooting over it.