Veteran
10% Critical Chance for every 0.3-0.45 second while aiming. Stacks 10 times. Discharges all stacks upon firing.
Weak Spot Hits gain 20-50 Cleave.
Get hotshot rank 1. It is bugged and multiplies the enemies hit mass by 0.2. Rank 4 multiplies it by 0.5 which makes their hit mass higher.
You have 5 points to spend where you want. I would recommend Demo Team, and to avoid perks that increase ranged damage; you already hit all breakpoints.
For Curios I would recommend as many Stamina Curios you can get away with (1-2), and Toughness Curios for the rest.
I would recommend all Curios include Stamina Regen on them. It helps a lot.
Any melee weapon works, but I would recommend one that can deal with hordes efficiently.
Below I will link a similar build that is finished, but uses Voice of Command for anyone that doesn't want to make their own build.
https://darktide.gameslantern.com/builds/9f73ea39-699f-4764-ace0-6c5587e217e2/hellbore-inf-ammo-crusher-1-shot
Below I will link another 1 shot Volley Fire build that has 10 points to work with if you need more.
https://darktide.gameslantern.com/builds/9f73f277-4653-4e11-9303-fcec9c9f01e1/secret-hellbore-1-shot-build