bry,
If your lucky like me, and have more than a few receivers, you can probably get by swapping barrels without ever having to do a fitting job. If a barrel doesn't fit a certain receiver, I just switch it to another, usually, after swapping between two receivers, I find one that fits.
"The reason I'm asking is that my2002 Huntsman's barrel is starting to show some corrosion and I'm thinking about getting a spare. If I don't need to send the reciever in that would be one more reason to go ahead a buy an extra." What happened here? That question isn't a criticism.
By all means go ahead and buy that extra Huntsman barrel for use as a spare. I honestly think that you could clean up the "corrosion" by a good cleaning with boiling hot soapy water. I helped an older friend with a Sidekick that he purchased used, and when he got it, the gun was a mess. Spent a lot of time trying to clean it with traditional BP cleaners. It cleaned most of the gunk out, but it still looked like the barrel had pitting/corrosion in the barrel. Finally we used hot soapy water, and gave it a good scrubbing, then rinsed it off with clean boiling water. Dried it off and left it to air dry. The barrel came out spotless, and the "pitting/corrosion" was gone. Remember, it has to be boiling water, not hot water from the tap. That water isn't hot enough. Wear gloves on the hand that is holding the barrel, as the heat transferred from the boiling water to the barrel can be quite uncomfortable.