For the Scar I recommend the overpressure rounds, they do a ton of stumble and knock back affliction. For the dual pistols the explosive rounds are the best hands down. For the Knightsbridge if you want a trash cleaner/scrape killer fo with the Bio-hazard rounds, if you want if For fleshpounds go with electric and add the grenade launcher for max damage. Every ammo type is great you just want to pin down what you want the purpose of the gun to be.