[tmax63]

If I had to pick a single caliber rifle it would be a 30-06. Very wide choice of ammo available and if you roll your own (reload) the options get even bigger. You would be hard pressed to find anyplace that sells ammo that wouldn't have '06 ammo on the shelf. Remington, Ruger, Savage, Winchester, there are tons of rifles around new and used. Very few rifles are shot enough to wear them out so don't be afraid of used. If the barrel is bright and clean an older "off-the-record" deal is hard to turn down and harder to trace. And a 06 would be fine for everthing that you could run across in North America although a little light for the biggest bears.