This build/guide is about Cedo Prime calcs/DPS, and is only 2-3 Forma on Prime depending on your Exilus choice (or lack thereof).

HM Slot: [Magnetic Strafe] OR Shotgun Barrage also work. But, see my reasoning for HM below!

This weapon has innate GunCO and mulitiplicative GunCO -- I'm not sure if the Warframe DPS Calculator accounts for the innate part. https://warframe-damage.com/

[Hunter Munitions] is perhaps being overlooked since the Slash nerfs. I think it's still really good on the [Cedo] (Prime), because nearly every shot procs Slash with Critical Deceleration due to the very high base Multishot, increasing further with external Crit Chance and Multishot buffs. Alt-firing the Glaive and then simply shooting the primed targets results in some very nice scaling DPS. An additional Status for the double-dipping multi-GunCO is proving highly useful in testing over other slots.

I highly recommend running Citrine, Saryn, Gauss, Wisp, Harrow, Xaku, Rhino, and of course Lavos -- or other weapons platform frames. [Citrine] in particular is hilarious and awesome with her Prismatic Gem and Crystallize.

Cedo Prime and Multiplicative CO calcs:

• vs lvl 200 Corrupted Heavy Gunner (Steel Path, Eximus)
• Viral Stacks (primer/Panzer) or Nourish required (both result in roughly equal DPS at a 65% Nourish vs 10 stacks of external Viral)
  For this set of calcs we are going with external Viral procs. Nourish results in roughly 1-2 million less DPS than priming, but it really doesn't matter much at all.
• Manually selected 9 Status (Heat, Corrosive, Puncture, Slash, Toxin, Electric, Cold, Magnetic, Viral)
• No Primed Ravage, Shotgun Barrage, Fire Rate buffs
• Multiply by about 1.5x for Arcane Tempo buff
• Multiply the DPS by 10 for your Headshot Multiplier

Armor:
Normal Attack
Random queue dps:
4,845,857

• avg per shot (without status dmg): 41306
• avg per shot (status dmg): 7494
• avg per shot (total): 48800

Health:
Normal Attack
Random queue dps:
6,801,083

• avg per shot (without status dmg): 60943
• avg per shot (status dmg): 7548
• avg per shot (total): 68490

With external crit (Avenger + Adarza):
Armor:
Normal Attack
Random queue dps:
17,225,675

• avg per shot (without status dmg): 86624
• avg per shot (status dmg): 16354
• avg per shot (total): 102978

Health:
Normal Attack
Random queue dps:
24,306,074

• avg per shot (without status dmg): 127218
• avg per shot (status dmg): 16851
• avg per shot (total): 144069

Other Options:

• Primed Charged Shell, but Shell Shock is pretty valuable due to Status Chance
• Blast + Elementalist with Primed Cryo Rounds
• Almost any other Primary Arcane works just fine. Crux honestly didn't feel super amazing but I could just be bad.
• Can replace HM with Magnetic Strafe for more up-front damage and bigger Heat ticks and Alt-Fire ticks up-front, or as mentioned, Shotgun Barrage (which can also replace Magnetic Strafe or Arcane Tempo)
• Can also replace HM with Shotgun Elementalist if HM just isn't for you
• [Narrow Barrel] or [Spry Sights] in the Exilus as Galvanized Acceleration and Fatal Acceleration are somewhat overkill for the falloff this gun has already, plus the seemingly buggy alt-fire Glaive with increased projectile speed
• This can be pushed even further with Fire Rate buffs from Arcane Tempo, [Reinforced Bond], [Wisp], [Gauss], and abilities such as [Thermal Transfer]'s Blast damage donation