This build is a Hybrid Self Priming DPS build for Grineer/Corrupted as well as other faction variants listed below. Uncharged shots on Epitaph has a large AOE and high status chance, allowing you to proc blast, cold and viral in AOE and impact/puncture/slash on direct hits. Charged shots have high base damage, very high critical status and multiplicative CO scaling allowing it to deal obscene amounts of single target damage, as well as forced impact allowing you to take advantage of Hemorrhage for bleed procs which ignore armor of Grineer/Corrupted units.
MOD BREAKDOWN
Galvanized Shot: Mandatory +dmg which is MULTIPLCATIVE to Hornet Strike/Merciless/Precision on Charged shot direct hits, giving +120% dmg for each status. If you prime with uncharged shots first, you can proc impact, puncture, slash, viral and cold status which gives +600% damage. Also boosts status chance for uncharged shots.
Galvanized Diffusion: Mandatory +multishot
Primed Pistol Gambit/Creeping Bullseye/[Target Cracker]: Mandatory critical chance and damage mods.
Note: I have used [Creeping Bullseye] to fit other configurations that require a naramon polarity. Having +60% fire rate from an external source such as [Reinforced Bond] or +45% fire rate from Amalgam [Furax Wraith] gives free fire rate that puts you JUST under the threshold for [Hemorrhage] when used with [Creeping Bullseye]. Using [Primed Pistol Gambit] with [Reinforced Bond] exceeds the fire rate 2.5 threshold
[Pistol Pestilence] + [Frostbite]: Makes Viral and boosts status, allowing uncharged shots to apply viral status quickly which boosts all damage to health by 2x at 1 stack and 4.25x at 10 stacks. The raw viral damage also has a bonus against Corrupted enemies.
[Hemorrhage]: Gives 70% chance to apply a slash proc, since [Epitaph] charged shots have forced impact. Slash procs bypass armor. You just need to keep this under 2.5 fire rate to have the maximum chance, which means you cannot slot [Lethal Torrent] or use Reinforced Bond (1.75x1.6=2.8) UNLESS you run Creeping Bullseye (1.75x1.4=2.45). If you are stripping armor via corrosive/heat or via abilities, you can swap [Hemorrhage] for [Primed Heated Charge] instead for a raw damage variant.
Primed Expel: Applies a +55% bonus to a specific faction, but is MULTIPLICATIVE to both Galvanized Shot and other dmg mods like Hornet Strike/Merciless. Faction mods also apply twice to DoTs such as slash, giving a final 2.4025x multiplier.
Arcane
Very situtational:
Primary Merciless: Gives +360% damage which is multiplicative to Galv Shot, and can be activated on slash DoT kills. This is the best general use option
Primary Deadhead: Also gives +360% damage as well as 1.3x headshot multiplier, but is more difficult to proc via slash DoT kills.
Cascadia Flare: Gives the highest possible base damage bonus, but requires you to proc heat either via the weapon (means you need to add a heat mod) or externally via another weapon/warframe.
Secondary Fortifier: Boosts damage against Overguard and also allows you to steal overguard. This is a very useful arcane to help with survivability as well as for fighting eximus/Thrax, but requires you to add base damage in another form such as [Hornet Strike] or Arcane Precision.
Secondary Surge: Gives the highest possible damage multiplier of up to 8x for a single shot which is MULTIPLICATIVE to other base damage bonuses, but requires you to add base damage via Hornet Strike or Arcane Precision.
VARIANTS
Thrax/Cascade: Since Thrax are factionless and have significant overguard, swap Primed Expel for [Hornet Strike] and use either Secondary Fortifier or Secondary Surge.
Raw Damage with External Strip: If you prefer to use raw damage to kill rather than rely on slash proc, and have some form of armor strip (either via external corrosive status or ability), swap [Hemorrhage] for [Primed Heated Charge] to make Viral Heat and Merciless for Cascadia Flare.
Raw Damage with Nourish: If you prefer to use raw damage to kill and are running Nourish, swap [Frostbite] for [Primed Convulsion], [Hemorrhage] for [Primed Heated Charge] to form Viral Corrosive Heat, and swap Merciless for Cascadia Flare.
Raw Damage for Murmur: For murmur, swap [Hemorrhage] for [Primed Convulsion] to make Viral Electric and swap Expel to Murmur.
Raw Damage for Corpus: For corpus, swap [Hemorrhage] and [Frostbite] for [Hornet Strike] and [Pathogen Rounds] to make pure Toxin which bypasses shields. Can use Secondary Surge or Fortifier if you prefer.