[Borderlands 3] Farming Katagawa Ball for the Brainstormer

I REALLY wanted a Mayhem 4 Brainstormer! Like, for realsies! Best source for this gun is Katagawa Ball, in Skywell-27. MH3 Stark Krakatoa ("sniper" -- more of an OP assault rifle to me) MH4 Expert Hellshock (pistol) MH4 High Capacity Warlord (assault rifle)