This is an absolute unit. It will tear apart everything in sight within a few seconds.

WARNING

Priming is absolutely necessary for this build to work well. Viral is the king, but get as many status effects on the enemy as you can since [Galvanazid Aptitude] scales from the number of different statuses. I recommend you use [Epitaph], [Kuva Nukor], [Tenet Cycron], or a Hound for priming. With the right primer (Secondary Encumber), it can generate and maintain a +1,040% damage boost. Huge, right?

How does it work?

Fulmin has a guaranteed impact proc in semi-auto mode. On its own, the impact is not that great, but force impact is a whole other story. It synergizes well with the [Internal Bleeding] mod which adds a whopping 70% chance to every shot we take to proc an additional bleeding status. And this will be our main source of damage for this build.

The bleeding deals cinematic damage, which bypasses the enemy's armor. So it will scale well into the steel path and with the right setup it can easily carry you into the level cap.

Also, [Galvanazid Aptitude] damage is multiplicative on the semi-auto shots, which enables the BIG BANG part of the build. (kudos to Master2873 for pointing this out)

Why [Terminal Velocity] is here?

[Fulmin] has linear damage falloff from 100% to 33.33% from 10m to 20m target distance, limited range of 20 meters, and guaranteed impact proc to enemies up to 9 meters.
All of the above is affected by Projectile Speed, and that's why we use [Terminal Velocity].

Why Primary Merciless?

Primary Merciless comes with a 30% reload speed boost which brings reloading delay down to 0.5s. And for the Filmin that's a huge difference in how this weapon feels.

Why not add [Hunter Munitions] to proc more slash?

Because [Internal Bleeding] and Hunter Munition procs are mutually exclusive!

Here is a quote from wiki:

Procs of [Hunter Munitions] and [Internal Bleeding] are drawn independently, and if both proc at the same time, only 1 slash proc is applied. With both mods, if a shot both crits and applies impact status, the probability of slash proc is 54.5% (with attack speed > 2.5) or 79% (with attack speed <= 2.5).

In other words, adding [Hunter Munitions] adds an additional 9% chance of slash procs, which is a waste of a mod slot.

Rotation

So here's what your rotation will look like:

• Prime a group of enemies.
• Shoot 5 bastards in the face. (body-shots are OK, but headshots will ramp up the [Galvanized Scope] which adds +200% crit chance)
• Watch how everything dies regardless of the faction.
• Repeat

Riven? Riven!

You can swap [Heavy Caliber] mod for a decent riven that gives your crit chance/damage and multishot.

Flexible Slots

• You can swap [Heavy Caliber] for one of the faction mods if you run endurance or just don't enjoy life in general.
• If you either struggle to get the headshots or you don't want to use the scope, [Galvanized Scope] could be replaced with [Bladed Rounds]. But I strongly recommend keeping it as it adds way more damage even with occasional headshots.
• If don't want to use secondary primer and you have something like [Panzer Vulpaphyla] that primes with viral, then you can swap [Galvanized Aptitude] with [Bladed Rounds]

Have fun!