If you can afford the elk hunt, then you can afford a .30-06.....gunbroker is full of them and with a little patience you can get a very serviceable gun for well under $350

Will the .243 kill elk?....of course it will, but if you don't get that broadside rib cage shot at 100 yards and are forced to take a very nice bull quartering away from you, you'll be very happy to be throwing a 180 grain bonded bullet. Call it an insurance policy if you like.