S&W uses to two variations of the barrel - shroud construction.
As mention murphydog , we have a separate shroud, barrel, and end cap or barrel nut.
In the other the barrel has a lip, so just a barrel and shroud. A crush washer under the lip is also used to allow assemblers to get the correct BC gap.
All the X-frame offerings are of the above described construction. methods.
Pictures of a variety of 460 S&W barrel and shrouds