30-06
in wy the minimums for buffalo are
270 caliber or larger
150grs or more
a .45-70 is very traditional option, lever action, but if you've never hunted before, and will be making a 1st big game rifle purchase, a 30-06 can hunt most of North America quite well, it's also big, but not too big to where it would scare your or your wife probably, like a 300+ mag would.
a .270win. or 7mm Rem.Mag. would be also good choices.
Last edited by salukipv1; 10-20-2011 at 08:15 PM.