powderburns: if it shoots the 308 just fine and with good accuracy it must be rebarrelled in the 308 caliber because none of the K98s were issued in anything other than the 8mm Mauser caliber. There is a Mauser rifle out there that was chambered, or rather re-barrelled in the 308 caliber from the original 7mm Mauser caliber and it is one of the South American Mausers.
It is not a 7.62x39mm - the 308 cartridge would not/does not chamber in a rifle in that caliber. All Mausers are top load bolt eject, unless you drop the magazine floorplate but using the bolt to eject is a common practice. I'm willing to bet that what you have is either a rebarrelled K98, if it is a K98, or one of those South American (forget what country) 7mms that was rebarrelled to 308. HTH. Mikey.