Identify this cartridge?

triceratops3

Sergeant
Full Member
Minuteman
Dec 27, 2010
738
1
31
Northern VA
I was at the range the other day and found these shells but I don't what they are.

They're 2.2" long and around .485 wide at the rim. The mouths are .299-.3" inside diameter.

here is a picture of two of them next to a .308 win.

100_2433.jpg


and here is a picture of the headstamp

100_2429.jpg


Any ideas? Thanks