Based around Big Seven for strong AP and HE damage. I personally didn't choose the legendary because I don't like the negative effects of these two but for the sake of this builder you have to. If you want to pick one then go a head. Chose Firefighter over Marksmanship just to have the best rudder shift possible but you could go either way. If you don't want Big Seven there's Gyrating Drillbits as an option.