S Tier Build
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I decided to put this build here because on weapon tiers on overframe.gg I noticed that many players that use this site don't seem to realize the power of [Amprex].

[Amprex] coupled with [Ignis Wraith], have been the best AoE DPS primaries for many years now and still have that place on the top.
While [Ignis Wraith] is better than this on wide open areas and longer corridors due to conical AoE and longer range, [Amprex] is better on closer quarters and tight corners since it chains in all directions (including up and down). Ship tiles are great for this weapon where you can see the sheer power as if you were nuking with your warframe.

Note: Bleed builds aren't good versus Sentients due to their immunity to bleed.

Some Math

Fire Rate+MS:
22,8 shots on sustained fire

Status:
24,2% to proc Viral
10,9% to proc Electricity
80% CC
4,8x CD

And a chance on top:
+24% to proc Bleed (on a 4,8 multiplier scaling with viral and faction mod and % Vigilante set)

As you can see the scaling is better than most WF weapons.
[Ignis Wraith] loses more DPS than [Amprex] on Steel Path due to it's lack of a reliable bleed (ignoring all armor and armor bonus) the heat can't keep up with it.
Exactly 24% of the shots proc bleed on each enemy it hits while also possible adding Viral/Electric, 2 procs per mob hit.
Before Status Chance above 100% was a thing, this already existed.

Main drawback, reduced 1st target range.

Alternative Mods

On lower level mobs you don't need to rely on [Hunter Munitions], in fact it's faster to kill without it due to lower armor and higher raw dmg.
If you are missing some mods or capacity before the full build you can use other alternatives but your DPS will suffer versus high armor values.

Options:

[Heavy Caliber]
[Bladed Rounds]
[Vile Acceleration]
[Vigilante Armaments]
[Rime Rounds]

The formas on weapon allow you to have multiple setups. So you can have this setup and a RAW DMG as well.

Note: There was a time when this weapon could make good use of [Sinister Reach] and [Primed Shred] since it applied the range and Punch Through to all rays, but now it only affects the main shot. This should hint you how OP this has been that it needed a "fix" reducing it's AoE.

Riven

Due to the disposition it's hard to get a Riven that has a slot here.
A great Riven for this is +Dmg +CC +CD -Zoom (or other negative without impact).
It's not easy to roll a Riven like that, but if you manage it not only increases your DPS, it pushes your CC above 100% meaning that 30% of hits proc bleed per hit

Future

No Vandal or Prisma [Amprex] was released...
Can we get a Queen [Amprex] on corpus Queenpins? ;)