smooth twist X barrel assembly?

Greetings,

Regarding the smooth twist X barrel, I know the brass TP portion of the barrel unscrews, but how about the silver portion it screws into? Does that unscrew from the black tube on the barrel? I'm assuming it must, because with the borescope I can see that there's an o-ring way up in there that fits around the outside of the liner. That o-ring would be really hard to replace if that silver portion doesn't unscrew. Is there a drawing that shows the ST-X barrel assemby? I only see the one for the ST. 

Thanks,

Rusty