Simple 3 forma build. In my opinion, no additional forma is needed unless you want to mod on [Stabilizer] into the exilus slot.

I tested this weapon in both full crit (with [Hunter Munitions]+[Hammer Shot]) and with pure damage mods but this specific status builds outranks them all (very efficiently clears steel path).
Mainly due to its innate AOE proc which already contains viral - making the weapon proc VIR+COR+HEAT (OP with Galvanised Aptitude).

This build was designed for minimum forma requirements so there aren't really any build alternatives unless you are willing to use a rank 4 [Malignant Force] or forma further. In that case, using [Hammer Shot] or [Hunter Munitions] or a RIVEN can be used instead of [Thermite Rounds] (does decrease the damage and AOE armour strip).

I run this with Arcane Acceleration on my warframe but if you prefer you can run [Vile Acceleration] on the weapon to increase the fire rate (drastically decreases damage).