Run a search...this question has been asked and answered...a few times at least...the cartridge is a 500 Alaskan?

(can't remember, Tim will know). It is basically a 50 Alaskan using the correct size bullets for the barrel...dies and reamers are available.
It is do-able...but you're not going to like the recoil level unless you increase the weight of the rifle by a bunch... I've though about doing a stub barrel about 28-32" but the building costs vs what you end up with keep me in the "thinking only" stage..
You also have to be aware of the pressure limitations due to the larger diameter cartridge head diameter 0.553"...rim dia slightly larger than a 45-70 at 0.608" plus or minus the usual fudge factor, but being a custom loading proposition that shouldn't be much of a problem if you keep your wits about you.
The major problem is the die and reamer cost vs the actual gain in ballistics...it costs you a bunch to get a little in reality, and there are several other ways using using rimmed and/or rimless cases to REALLY get some pizzazz.
The 500 S&W has enough slaparound as it is and if you load it with 500 plus grain bullets not many want all that you will get from both ends anyway...besides going with the larger diameter case head will lead you down the "walking on the wild side" path...as far as pressure is concerned.
Luck on your project.