mossberg shotgun bbl locking collar question

[badboybeeson]

Does any ones know if the bbl locking collar on a Mossberg 500/590 etc is a separate part or it is machined as part of the barrel the way Remington 870.11-87 is
I know Benelli,s are screwed on but cant tell if Mossberg is the same
bbb

 

[gunrunner100]

I was always under the assumption that they were soldered onto the barrel.