1. Put Blast on Resupply(2)
2. Place Antenna(1)
3. Aim to the head(Open Scope to get 50% crit chance and to help Bladed Rounds)
4. Watch Eximus AOE one shot

Build Information:

As wiki says:

• This weapon deals pure Electricity damage.
• Charge-up is automatic and will automatically fire unless the trigger is held.
• One zoom mode that has 8x zoom distance and +50% critical damage.
• Reloading does not break zoom, unlike other sniper rifles.
• Damaging a target has a ?% chance to spawn 1 - 3 lightning strikes on nearby enemies, dealing 400 Electricity damage.
• Damage and status effects are affected by equipped mods.
• Damage is not affected by Galvanized Aptitude.
• Number of lightning strikes is affected by Multishot, Punch Through, and Blast status effect.
• Can perform critical hits.

To achieve better results with this weapon, punch through and fire rate added from Primed Shred, Blast comes from Resupply, you can ask about multishot-lock from Primary Acuity, you are right but since this is Cyte Arsenal weak-point much easier to hit and reward is higher than other frames due to Practiced Aim passive.(Up to 300% additive crit chance max per mission)

SInce lightning can perform critical hits, it also triggers headshot on some enemies as far as i can see. So if that lightning kills enemy Galvanized stack will be much more easier. Thats why i added [Critical Delay], [Vital Sense] and Bladed Rounds.

Status chance seems to be not affect lightning strike spawn chance so we are running Stormbringer here not 60/60.

[Vigilante Supplies] is optional, but if you have Sentinel it can achieve extra tier with 20% chance.

Lastly [Rifle Elementalist], increasing Elec + Blast damage also gives punch through.

Stacked Demonstration(Arcane Crepuscular equipped)