Monsterf*cker
 Veteran Build - Warhammer 40k: Darktide 

This is a build with designed for using the boltgun in the most efficient way possible, trivializing all elites and bosses.

Try to get 65% or under mobility on both weapons to maximize their potential.
 

Playstyle:
Your task will be to target all ranged enemies, elites, ogryns and bosses. Everything you want to kill, you should mark, to get continuous damage stacks so I recommend binding the ping target key to left alt or any other key you find.

For elites you can just one tap them with your bolter as you mark them, hit anywhere and they'll die. If the shot doesn't kill them, the bleeding will.
On all ogryns, 3 shots to the head will surely kill them. 3 or 2 shots to the head or body for maulers, depending on whether you crit or not.

Shoot with confidence. This might seem like it's ammo hungry, but with scavenger, and you effectively one-shotting every ranged enemy you come across you get about 1/3 of your ammo back with every encounter.

Bosses: 

It's straight forward. Mark them, Use your ultimate, magdump twice into their weakspots. That's it, the boss is gone.

Hordes: 

The shock maul will make up for any lack of points invested into melee talents, with it's high stagger and damage. There's really no situation the shock maul can't handle
Horde in front of you? just spam light attacks. You can literally bulldoze through. If you have the space for it, sprint and charge your heavy attack for a powerful sweeping right to left.
Crushers and Maulers in front of you? Mark them, hit them with your special, bash their heads in with 1 or 2 heavy attacks.
Ragers? throw a grenade at your feet,  bash their heads as they are on the floor.
Bulwark in your face? use your special, bash his head in with 2 heavies. If you have your boltgun out you can dump 7 rounds into their shields around center mass to kill them 
Mutants? Mark them, 3 to 2 shots to the face should do it

TLDR:

Pros: You deal with most elites and specials in record time, the supression of your gun lets you solo a gunner squad.
Decent crowd control.
Excelent for erasing bosses

Cons: Low survivability skills, limited build variety.
No Voice of Command, the most powerful ability of all.