[Serration] for damage

[Vigilante Armaments] because multishot

[Vital Sense] for critical damage

[Critical Delay] for critical chance

[Galvanized Chamber] for more multishot

[Galvanized Aptitude] for more damage

[Hunter Munitions] because it's broken

[Vile Acceleration] because there's not much else to put there really. You could go for a primed bane like [Primed Bane Of Grineer] but that's if you want to switch it out for "every" encounter. Really you're doing that if you go high level anyways and Grineer are the easiest at high level so slap it on I guess.

This doesn't consider arcanes like Primary Merciless which basically means [Serration] is useless so you'd switch it out for your bane mod instead of [Vile Acceleration]. Or you can take off [Vile Acceleration] and [Serration] and use [Primed Cryo Rounds] and [Infected Clip] or [Malignant Force] and [Rime Rounds] to mod for viral.