Re: What does changing a guns caliber entail?
Because you are asking the question I can "assume" you are in the same knowledge boat as most of us and you will NEED a gunsmith to do the work for you. He will either re-bore and re-rifle your barrel (not a good choice) or you will buy a barrel in the caliber you want, the smith with cut the threads, crown it, cut the chamber you want and install it in your reciever. I "THINK" you are looking in the $100-$200 range for the work (I might be way off, there are others here who would give you an exact quote) plus the cost of the barrel. While he's got it apart you might as well have the action blueprinted also. The cost of the barrel could range quite a bit depending on exactly what you want and what you want out of it.
Another thought; as long as you are doing this you might also think about a different(wildcat) cartridge that will fit into your action. 30 Gibbs, any of the Akley Improved, one of the short mags.....
Good luck on your project. There are lots of people here who will be able to offer lots of help if you need it.
Genises 27-3: Now therefore take, I pray thee, thy weapons, thy quiver and thy bow, and go out to the field, and take me some venison...