Barrel has a nut, but it's not the same system as the centerfires. Couldn't be as the rimfire actions are a lot smaller in diameter. It's a smooth nut with no spanner hole or anything, so a special wrench will be needed.
The other major change is that the breech of the barrel is now coned so no need for extractor cuts that require the barrel to be indexed. As such it should make for a rimfire platform where you can easily swap on a quality aftermarket barrel just like a 110 or Axis.
Attachment 3026