Space Marine Charge & Rapid Fire
When a model is armed with multiple separate ranged weapons, you only have to follow the restrictions of the ones you use.  So if you choose to fire your Bolt Pistol instead of the Bolt Gun you are free to charge in the same turn.  Pistols have no restriction against assaulting after using them.  

If you choose to fire the bolt gun at either its full or rapid fire range you cannot assault.