RE: Need some help from experienced hunters please
As others have said you can pretty much forget finding one riflethat will do everything. Any rifle cartridge that would be consistently reliable in stopping a grizzly charge would be ridiculous overkill on rabbit sized game. And any cartridge that wouldn't explode a rabbit like a watermelon would be way too small and underpowered for Grizzly.
As stated above the one gun that would come the closest to letting you hunt all game in at least some fashion would be a 12 gauge shotgun. Bird shot for dove, quail etc, 6's for rabbit and squirrel, 4's, 5's or 6's for turkey, 4's, 2's or BB shot for ducks and geese, and slugs for all the medium to large 4 legged animals. But a smoothbore shotgun will only fire a rifled slug accurately out to a pretty short range and because of that I would not want it to be my only hunting gun. But ifI had tostay in the woods and live off what I killed with only one gun for a year then yeah, a 12 gauge with a variety of shells would be my choice.
The 30-06 is a fine choice for a good all around cartridge.I wouldn't want to use it as a small varmit caliber for things like prairie dogs (too much recoil) but from coyotes up to moose and elk it would be fine. Probably more bullet choices out there for it than any other cartridge. That said however, a good well constructed 165 grain bullet that your particular rifle grouped well would be all you needed to cover the whole range of animals I just mentioned.
As for rifle type? Me personally I'd rather have a bolt action. Semi-autos do offer a quicker second shot but a lot of them, particularlythe cheaper ones,do suffer from jamming problems if you aren't pretty meticulous about keeping them clean. Some still jam even if you are. The BARsemi-auto made by Browning has been the most trouble free of any that I have had dealings with. On the other hand bolt actionsrarelyhave any feeding problemsand they are also typically more accurate. You don't have to spend a lot of money to get an accurate and reliable bolt action either. Savage makes some good ones at a very economical price. That would leave you with more money to buy a good scope whichI consider as important if not more so than the gun itself.
Good luck, and keep us posted with what you choose.