When I began loading for my .375 Ultra, one of the first loads I devised was a 260 gr Ballistic Tip at 2600 fps. This load was accurate, mild in terms of blast and recoil, and would shoot flat, so if I ever managed the opportunity to hunt Dalls, that was what I intended to use. Since then, the delicate 260 gr BT has been replaced with the tough AB, sheep hunting seems to have become more elusive due to cost and the fact that I'm not getting any younger, and my sea level lungs quickly point out my limitations at altitude. For those who might suggest that a .375 Ultra is a ridiculous cartridge for sheep hunting, you are correct, but despite that, it works and I have used it enough that I'd confidently use it against any terrestrial game. Anyone recall the Chadwick Ram? That 50" monster was taken with a .404 Jeffery, the granddaddy of the .375 Ultra.
About the same time that Mr Chadwick rugged his famous ram, a youngster named Jack O'Connor was defining the most successful sheep cartridge to ever come down the pipe, the .270 Winchester, with his M-54 Winchester. If sheep hunting is the question, the .270 is the answer, although the M-70 and others have eclipsed the M-54. There are cartridges that can do the job as well as the .270, but none do it better. Even if the .270 is not your cup of tea, you should measure your choice against it. If it doesn't shoot as flat, if its heavier, if it kicks more, or if its more or less powerful, its probably not quite as good.