.300 Winchester Magnum

The .300 Winchester Magnum is a belted, bottlenecked magnum rifle cartridge that was introduced by Winchester Repeating Arms Company in 1963. The .300 Winchester Magnum is a magnum cartridge designed to fit in a standard rifle action.Wikipedia
 
Bullet diameter.308 in (7.8 mm)
Case length2.62 in (67 mm)
Rifling twist1:10 (254 mm)
Case capacity93.8 gr H2O (6.08 cm3)
Parent case.375 H&H Magnum
Shoulder diameter.489 in (12.4 mm)
Base diameter.513 in (13.0 mm)