.300 Savage

The .300 Savage cartridge is a rimless, .30 caliber rifle cartridge developed by the Savage Arms Company in 1920. It was designed to replace the less powerful .303 Savage in their popular Savage Model 99 hammerless lever-action rifle. Wikipedia
 
Bullet diameter.308 in (7.8 mm)
Case length1.871 in (47.5 mm)
Parent case.250 Savage
Base diameter.471 in (12.0 mm)
Rim diameter.473 in (12.0 mm)
Neck diameter.339 in (8.6 mm)