I guess I'm not sure why a sheep rifle has to have too many specific attributes that other rifles don't have.
I want all my rifles regardless if they are on my pack to chase sheep, bear, moose, caribou, mountain goat, deer or whatever to be the following:
1)Relatively light weight say sub 8 all up is nice (lighter than that is even nicer)
2)Short and handy (no thanks for any barrel longer than 24" (20" or less is even mo betta) as the rifles spend far more time strapped to my pack than in my hands and as such no one likes having a long barrel sticking up and catching on alders.
3)Reasonably accurate (ideally sub 1 moa is fine, sure 1/2 MOA is better no doubt but not needed) I know I am the limiting factor when it comes to shooting off my pack with my left foot slipping down the slope on the scree and a sharp rock is sticking into my gut while waiting for the animal to turn broadside. That 1/2 MOA of accuracy from 1 MOA to 1/2 MOA isn't really gonna be the make/break of any sheep hunt for me.
That said I am far from an expert when it comes to sheep hunting especially with only shooting 2 myself (both with bullet with BCs of well less that .5 let alone .6) and seeing 9 more killed and helped hauled off the mountain for other folks.
I honestly feel folks (myself included) spend FAR too much time worrying about their rifles/load/scope/gear and far too little time on actually getting out and hiking, learning about sheep, getting in shape, or even scouting on where they'd like to hunt sheep.
Reality is for me is that any rifle can be a sheep rifle, just like most any centerfire is a grizzly rifle if its the one I happen to have along with me at the time.