Here's what the Glossary says:
Quote:When this character combines fire with adjacent allies with Mounted Weapon, it grants the stated bonus to Damage on that attack. Enemies cannot use abilities such as Parry or Lightsaber Block to avoid that damage, Damage Reduction has no effect, and abilities such as Draw Fire or Bodyguard cannot change the target of the attack or redirect its damage. Likewise, abilities that reflect damage back to the attacker have no effect against that attack. Crack Gunner does not affect damage from effects that are not attacks, such as Force Lightning.
So it seems that yes, Crack Gunner +10 means no saves and no damage prevention at all. Nasty.