.308 Caliber Round (Fallout 3)

The .308 caliber round is a Small Guns ammunition found in the game. It is only used with the sniper rifle and its unique variants.

Characteristics
The .308 Caliber Round is the third rarest small guns ammunition found in the game, next to .44 round, magnum, and the BBs; very few enemies carry sniper rifles, and many are located in hard to reach places or have only a small number of rounds to be looted. A notable sniper is Arkansas in Minefield. The hunting rifle largely provides the same effect while using the much more common .32 caliber round, making the sniper rifle and variants limited in effectiveness until the player gathers a stockpile of ammunition.

Used in

 * Sniper rifle
 * Reservist's rifle
 * Victory rifle

Merchants

 * Various vendors such as Chief Gustavo, Flak and Shrapnel, Knight Captain Durga, Karl, Moira Brown and others will sell this ammo.

Map locations
you can also find some on some super mutant behemoths but its pretty rare on them