The Red Hand (Arquebus) - Double Barrel: Fires two shots before reloading, but has a reduced range. Guilty Conscience 2% Damage dealt and received on Kill until Rest (Stacks 20 times). Twin Slugs Knockback target within 4m on scoring Hit. Hands down the most broken item in the game right now. Double Barrel effect is almost doubling your dps by itself and Guilty Conscience stacks up to 40% dmg taken/recived. Very easy to get (12 lock difficulty chest in delvers row) Guilty Conscience buff works for other weapons, so it's possible to stack it up and then swap to another weapon (does reset on rest though).
Always true ? I test it few hours ago, don't work for others weapons.
The underline statement is fixed in one of the patch.