S Tier Build
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This is a great weapon either you focus on main fire or alternative fire.
Stats of both are too different though, while AUTO is CC+CD based, BURST is SC based.

The alternative fire is really fun to use, specially on hordes of enemies, so this build aims to get the most out of that.
The alternative fire lobs 3 grenades that add Viral to the elements you modded on the weapon. Viral is a great element to proc that allows you to deal extra damage. Most other grenade launchers have Blast, which is mostly for crowd control but makes enemies harder to hit, this puts this weapon on a niche of it's own.

Playstyle is clearing rooms with alt fire and main fire the few tankier that were left standing.

Alternative Mods

If you don't like to use faction mods like [Primed Cleanse Grineer] swap it for [Vigilante Armaments] or [Vicious Spread].
Keeping the Grenade theme there aren't many options on this besides modding for different factions. For corpus faction focus on Toxic + Radiation damage instead.

Exilus is not required, but if you decide to unlock it go for [Fatal Acceleration] or the new [Galvanized Acceleration], weapon is projectile based and has infinite ammo so nothing else helps the build.
The formas on weapon allow you to have multiple setups.

Riven

This is a recent weapon so I expect disposition changes.
For the grenade theme a great Riven would be +Dmg +MS +Useful Element -Zoom (or other negative without impact).
For main fire you'd want for positives +Dmg +CC +CD instead, but criticals don't benefit the grenades on 3% base CC.

Future

Let's hope we don't get "fixes" :P

Updated: Arcanes and new mods