The current model line is I believe the Finnclassic.

I believe the barrels between the Valmet, Tikka and Finnclassic are all interchangeable with some gunsmith fitting required.

The instructions for the gunsmith fitting are included as a sticky on the NitroExpress.com forums.

Assuming of course they are all the "same" model. For example the Tikka M07 is NOT the same. The 412/512 etc are all interchangeable given the qualification above.

I know new barrels might not fit 100% having stuck a new set on my receiver and needing a rubber mallet with a slight tap to get it out again.