With a cantilever mount it shouldn't make a difference unless you whack the scope on something when the barrel is off. That is the whole point behind the cantilever set up. You can swap out barrels from slug barrel to shot barrel and not have to re sight in the gun. Now if you were talking about a receiver mounted scope with a removable barrel then yes, in almost all cases you will lose your zero if you remove your barrel, even to clean it.

I know many people with 870 and mossberg 500's with cantilever barrels and they always hold zero after removing and re installing the barrel. And I'm talking guns that shoot around 2 inch groups at 100 yards off from a bench, not minute of deer.

Paul