Quite a few years back when i was younger,healthier and physically more fit i hunted the famous Marco Polo sheep which is greater in size than the bighorn.Found in the northern areas of Pakistan on the border of Afghanistan and China at heights of 15000 ft.& above this probably is the only animal in the world which is hunted at such elevation.To get to its habitat is a trecherous journey involving days of acclimitisation,traveling on Yaks,employing porters and carrying oxygen in case of emergencies.At 15000 ft. you have to re-zero your scope as it goes completely off(i still don't know why)and you need a powerful rifle,nothing less than a 338 win.or 300WBY mag.as the nearest shot is around 300 yds.and the strong wind causes considerable drift.
The entire journey took about 15 days of bone chilling cold,fatigue(at times i thought of shooting myself & getting it over with ).A shoot like this can only be done once in a lifetime unless you have a deathwish,but it was worth it.