I think a .338 Win. Mag. would be perfect for you. Ammo will be easy to find, and you have 200 gr. 210 gr. 225 gr., 230 gr., and 250 gr. bullets from many different manufactures to choose from.

I shot a pronghorn with my 340 Wby. Mag. using a 250 gr. Barnes XFB at 200 yds. the bullet went in the size of a pencel and came out the size of a quarter. I didn't lose any edible meat. Good luck.