The 6 mm Remington is the same cartridge as the .244 Remington, but rifles chambered for the 6 mm Remington have a faster twist to stabilize the heaviest bullets. It has a slightly larger powder capacity then the .243 Winchester. The 6 mm remington is a good choice for varmint up to deer and antilope. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.