Here's what I used for my Grand Slam:
Dall--.30-06, 150 Nosler Partition, one shot, dumped in his tracks.
Stone--7mm Rem Mag, 140 Nosler Parttion, one shot, dumped in his tracks.
Desert Bighorn--25-06, 120 Nosler Partition, one shot, ran 40 yds.
Rocky Mnt Bighorn--.284 Win, 140 Nosler Partition, one shot, did a back flip.
Look in your gun safe.....you already have a sheep rifle. They have no constitution and any whitetail cartridge will work. Only the desert ram was further than 150 yds, 280 yds in this case. Last Sunday, I also shot a trophy elk
at 280 yds in Arizona, but with a .338 Win Mag. I wouldn't shoot a sheep with a .22 calibre cartridge, nor a whitetail either. Dave