Take your best guess. If you're correct you'll get bragging rights.

Stumped?

30-06. 375/416 Rigby, 338 Lapua Mag, 50BMG

30-06 & 50 BMG are correct :-)

30-06, .416 Rigby, .408 Chey Tac, 50BMG

Hans, you win.

Dang, I thought it would take you guy's longer than that, oh-well. Short game.

Here is a PIC of the headstamps.

BMG -
What's a .408 Chey TAC?
R-WEST

Here's more info than you could dream of;

Two summary excerpts:

.408 Cheyenne Tactical� Cartridge.

This purpose of this 2000-meter cartridge is to deliver accurate, high kinetic energy to a target from a sniper platform as well as to replace the 7.62mm NATO cartridge, which is currently being used for the military's General Purpose Machine Gun (GPMG). The mission for the sniper round is to selectively remove lightly armored targets at great distances without collateral damage to non-military targets. The cartridge's advantage for a machine gun -- intermediate between the M240 (7.62mm NATO) and the M2 HB (.50 Browning) is that it provides greater kinetic energy and distance over the 7.62mm NATO cartridge, but does not have the weight disadvantage of the .50 Browning cartridge. The cartridge approaches the ballistic characteristics of the .50 Browning cartridge, but fired from a platform less in weight that the M2 HB. Contrasting weight by weight, the .408 Cheyenne Tactical� cartridge is a third lighter, which translates into a third more cartridges per unit weight.

The parental cartridge case for the .408 Cheyenne Tactical� is the .505 Gibbs, necked to .408" and with a redesign of the web area. Solid nickel copper alloy projectiles for both sniping and GPMG are being designed by Lost River High Energy Technologies (Arco, ID) using PRODAS 2000 software. - from EDM Arms Web Page

"Parent case: .505 Gibbs, slightly modified and strengthened.

It has a .635 case head diameter. 144 gr. capacity.

The bullet is a CNC lathe turned solid copper/nickel alloy bullet from Lost River Ballistic Technologies.

www.lostriverballistic.com

The BC out of the barrel is .903, but it steps up to around .913 at 2300 yards under standard air conditions. I know, stepping up doesn't make conventional sense. Let's say for now that performance is better than we expected and the bullet / barrel setup is being patented." -from biggerhammer.com by Dean Michaelis

Range report- http://www.snipercountry.com/Articles/408CheyTac.htm

Manufacturer- (Has two links from there)
http://www.edmarms.com/408.htm