I personally would use a good 12 bore pump-gun, 20" to 22" - not an autoloader - Rem M870 or Mossberg M835 or 500 (Benneli or other Euro maker must have one) with full rifled tube, using 2-3/4" slug loads (less recoil than 3") if possible - Brenneke would work for me, but I would prefer heavy round ball loads due to improved penetration.

Learn to use it, with practice you will be able to shoot more quickly with accuracy, than can be done with an autoloader.

Every one of my Riot Squad team members could do this.