If the bolt headspaces, you should be okay.  However, understand that over time, the bolt's lugs wear with the barrel extension.  I'm talking about the metal surfaces that come in contact with eachother.  Does this make sense?  This is why I typically keep bolts (not the entire carrier, just the bolt) and barrels as a pair.  It's not as big a deal on a bolt/barrel with only a small number of rounds through them.   It could be a bigger issue with a well worn bolt.

If you're talking about swapping just the upper receiver, you shouldn't have a problem.

Hope this helps.