The WinchesterRepeating Arms Company introduced the .300 WinchesterMagnum (7.62×67mm), a bottle-necked magnum rifle cartridge, in 1963. The ammo was based on the .375 H&H Magnum and adapted from the .338 cartridge that was introduced in 1958. The new round was made for the Model 70 rifle. Firearms enthusiasts expected the conversion and were glad to have…