My personal favorite trumna prime build using the base heat damage of trumna for a viral/heat setup

If you want to use bane mods swap out [Serration]
if you want to use hunter munitions swap out critical delay

IMO primary deadhead is better than merciless because of duration/# of stacks/going for headshots to charge alt fire anyway/-recoil buff (trumna has a lot of recoil)/[Trumna Prime] has 25% higher base magazine and 20% quicker reload than regular [Trumna] making the +reload speed buff of primary merciless less useful

Vigilante supplies gives a slight dps increase, but you may want to consider using stabilizer for -60% recoil because of trumnas large kick, ESPECIALLY if you decide to use primary merciless instead of deadhead.

Riven mods are probably not worth due to 1/5 disposition. My +multishot/+cold/+damage/+recoil riven technically gives me higher sheet dps with a regular trumna since it has 2 disposition, do with that what you will.

This weapon is really good with the new [Cyte-09] warframe due to his headshot multipliers and [Quick Reload] ability