The Vengeance gives all bullets fired a chance to trespass through shields. There appears to be no way to keep the special effect to itself, nor does there seem to be a way to stop it working from just unequipping, selling, dropping, or stashing it. Once the effect begins it'll keep going until the next time you load up.
I need to find a new Vengeance... the one I have right now is underleveled.
And yeah... no Quick Charge... 5 points in Cauterize instead of Aid Station/Overload... MLG! Lol. XD