Built by someone who actually understands how Slash works. I am using both [Internal Bleeding] and [Hunter Munitions] to double the total Slash procs. [Amalgam Serration] can fit in instead of [Serration]. You can replace Bane faction mods as appropriate or use [Heavy Caliber] instead. If you don't like to aim heads, then you can replace the [Galvanized Scope] with a raw damage mod such as [Heavy Caliber] or a critical mod such as [Hammer Shot], if you lack both then [Vigilante Armaments] works fine too. This is primarily a shotgun mode build, if you prefer the assault riffle mode then replace [Internal Bleeding] with any mod I have mentioned above. The Arcane is up to your preferences the shotgun mode has quite a big target spread so it can hit heads quite easily into orange crits and red criticals are possible with a critical chance boost. I am using Nourish for Viral but you can use a secondary Viral Primer too. I run this with my Nourish [Wisp] with Arcane Avenger so it's quite nice to use because I gain Red Criticals. The bonus fire rate isn't bad, a higher rate gives more chances to proc, and a lower fire rate increases the chances of individual proc anyway.

Enjoy :)