FX Smooth Twist X barrel system

As Long_Gun_Dallas says, the barrel housing is the same for all calibers from .177 to .30, for the Dreamline, Wildcat, Maverick and Impact. However, while original Dreamline shrouded barrels will fit the Crown, the new SuperLight barrels on the Crown (and some Dreamlines) do not use a barrel housing and are therefore not perfectly interchangeable. (Actually shrouded SuperLight Crown barrels will fit a Dreamline, but not vice versa)

Chris
 
The barrel liner shroud (black tube) is the same for .177-30. But you also have the correct size barrel connector (silver piece between the black tube/xfer port) and the liner lock nut. Those are different between the calibers.

FX generally won't sell you the barrel connector staying warranty only. Huma sells a caliber exchange kit with xfer port, barrel connector, liner lock nut, and probe. Oh, and you'll need to make sure you have the right size liner oring spacers as the liners are different diameters between calibers