700 Barrel Swap + Caliber Change

In a perfect world, yes. In reality, not likely. But, give it a try, and if your go/no-go gages tell you you're safe, then at least you know you are that close. The next factor will be to determine once it is safe if you are happy with the accuracy. I've built a number of 700s, and no two have ever been close enough that I could re-use the barrel from one on another with confidence. But, you could always have the action trued and a gunsmith add a thread to the barrel stub and set back the shoulder accordingly and clean up the chamber, if necessary. I did this on an old .243 and it turned out pretty well; shot better than before, but not as good as a new barrel blank would have. However, I did it on a .300WM 700 and it really improved.