User blog comment:PFC Arkalis/Battleblog 8: Build your weapon of choice/@comment-4052979-20110826062949/@comment-1990578-20110826165547

The attachment system is pretty much the same as MoH 2010's system (3 slots: optic, rails, barrel), but with more attachments per slot.

But I don't think you could have a suppressor and heavy barrel at the same time since they both modify the barrel slot.