If your Consumables inventory is full (at least on the xbox360) and you use an ammo synth, it will be consumed but not give you the ammo. This has forced me to use up vault space in the past, so it affects game play in a negative and probably unintended way. Please let the guys working on 1.1.1 know about this specific [glitch]. There still seem to be other reasons an ammo synth won't work, but this is one I have managed to duplicate in the past.