Nitrox,i've taken horned sheep(ram)with a 243,100gr.bullet at 200 yds.but i feel much more comfortable when i'm using a 270(130grs.) or a 7mm.mag.(150grs.)I've also taken ibex with a 243 but only out of neccesity and would prefer a larger caliber.With a caliber like a 243 you have to be very accurate while placing the shot as in the mountains you may not get a second one if you don't drop the animal with the first one.However with a 7mm.mag.even if you don't hit a vital organ you cause enough damage to maybe slow down the animal thus giving you another chance.