I have a gun on consignment which could be the answer to your need. You can examine it at.
http://www.drillinghotline.com/new.shtml

The beauty of the interchangeable barrel system is that virtually any caliber barrel can be added to the set, or the existing barrels can be altered to fit the shooter's taste.

The rifle barrel slides into the lower part of the monoblock and into a hanger at the muzzle. It is held in place by a set screw through the action lug. The European hunter can hunt roe deer with one rifle barrel and red deer and boar with the other one.

The American hunter can hunt turkey (where allowed) with the .222 combination, and deer or boar with the .30-'06 combination, particularly effective with a Brenneke in the shotgun barrel and 180 grain softpoints in the rifle barrel.

I actually used one just like this one in Africa and took smaller plains game (dik-dik, klipspringer, Tommies, Grants, impala) with the .222 barrel and larger animals, up to and including wildebeest with the .30-'06 barrel. It is a suitcase gun for all occasions.