This build is made around the idea that ideally you already have a secondary primer, I have builds for [Nukor], [Detron] and [Epitaph] specifically for this purpose.

Because we have a Toxin progenitor bonus, we can easily slot a Cold mod to create Viral, which increases health damage done by 325% at 10 stacks.

Galvanised mods are used here to give us extra multishot and damage per status, because of the lack of [Hunter Munitions], we can also opt for Galvanised Scope as Slash won't steal our headshot kills. While this isn't ideal as Slash is best buddies with Viral due to its ability to ignore armour, our damage output more than makes up for it.

We use [Bladed Rounds] over another crit mod as the crit damage conditional gives us optimal damage as we already have Galvanised Scope to fill the role.

[Vile Acceleration], while directly decreasing our damage, also boosts our DPS as we can fire more projectiles, more chances for critical hit tier increases from [Vigilante Supplies], as well as being able to constantly trigger Arcane Acceleration, while not essential to the build, will enhance it greatly.

With every kill, Primary Merciless gives us more damage, and at Rank 5, gives us more ammo, passively affecting how often we can shoot.

Finally, we opt for a Bane mod that gives us another 55% damage from our total modded damage, as well as double dipping into status in damage calculations. [Primed Bane Of Grineer] is optimal here though you can also use the more common, regular [Bane Of Grineer].

Other Factions:
For Corpus, Toxin bypasses their shields so we only have to deal with their smaller actual health, remove [Primed Cryo Rounds] for [Hammer Shot] or similar, as [Serration] would only give us diminishing returns. And simply replace the appropriate faction mod.

For Infested, Gas or Heat is their weakness, replace [Primed Cryo Rounds] for a Heat mod, as well as the appropriate faction mod. (Note: Gas is also useful against Zealoid Prelate and other infested bosses)