The .243 Winchester was derived from the .308 Winchester by sizing the case neck down to 6mm (.243). The .243 Win offers a flatter trajectory with the heaviest bullets being 100gr to 105gr. In .308 Win the heaviest bullets arenormally 180gr, though some manufacturers produce ammunition with heavier bullets. This means that the .308 offers significantly more stopping power. Some sources quote the .243Win to have 50% less recoil than the .308.