weather or not you'll need one will depend on a bunch of details about your configuration, as well as your caliber, etc.
generally speaking - it cant hurt to have one there - but putting your upper back togther without one may end up with you being in a situation of overgassed, possibly quite badly, when shooting suppressed.
so since there's no down side to installing one added to the possibility of needing one once you do go suppressed, you might as well order one and get it installed now to save tearing things back apart later if you find out one is needed.
HTH
