I'm facing a Legion Centurion with 13 DT, using a Lever Action Shotgun which has 9.1 damage per pellet. With Shotgun Surgeon I'm supposed to be able to bypass his armor and deal substantial amount of damage (42 at least) but somehow shotgun surgeon doesn't work. The red shield appears and I only reduce his health by 8 at a time (7xbleedthrough). What is happening?