Axe's Stubber Build
 Ogryn Build - Warhammer 40k: Darktide 

It didn't seem like it should work, because historically Stubbers haven't been in a great spot (and they still need improvement) but frankly every time I've taken this build lately I've topped damage, so maybe there's genuinely something to it.  It does require precise aim (and even with precise aim the weapon itself isn't especially accurate so not even headshot will land).

Basically

1. Try to avoid shooting much without your ability (which provides 50% refund of all shots fired).  And don't take the build into "no ammo pickups" missions at all (and advocate for the removal of those missions, which are genuinely the worst Maelstrom).
2. Always aim for weakspot hits (due to your Stubber's blessings), prioritizing specialists/elites. You can and will shoot hordes with this too, but I try to only take shots if I"m hitting at least 2 horde enemies (and I'll switch to melee if the horde is dispersed enough that there aren't any good shots)
3. Be quick with dodges or switching to melee to push if you hear incoming attack sounds. The braced touhgness regeneration is nice, but you shouldn't rely on it to tank melee hits.
4. When Crushers close, a big fat charged Power Maul hit to the head will eliminate or critically wound them (and also everybody within a fairly huge radius), so use your Pmaul special whenever it's up especially if any armored targets are around (and "armored" in this case even includes enemies like the flak horde dudes; you get big explosions on quite a few types of enemies, it's mostly just the unarmored horde guys that fail to qualify)
5. Be extra careful against big single entities like Monstrosities, because the build lacks Smash 'Em! (although we partially make up for it with Confident Strike ).
6. Frag Bomb should be saved for when you think it'll be one of the biggest enemy armor pushes of the mission.
7. Technically you don't actually get horrible DPS by headshotting Crushers with your ranged weapon (900 - 1900 DPS depending on buffs or whether Burst Limiter Override  is active), but you should only do that if you're alright on ammo because it's pretty wasteful.
8. This weapon loves line-horde situations. So if you get enemies running around a corner lining up in a row for your shots, take advantage of the weapon's high Cleave values.
9. Weakspot hits always matter. So even though a body shot will kill a basic horde enemy, a headshot will give you a stack of headhunter (if you don't crit) so even against enemies that might not need to be weakspot to eliminate them, you should keep Headhunter stacks in mind because you might like a guaranteed crit (with that juicy +100% weakspot crit damage from Deadly Accurate ) for whatever you shoot after your current target!

Because of its reliance on weakspot hits, I doubt this will perform well unless you have good aim. But plenty of players have better aim than me (you can watch my vids to plainly see that) so it's still going to perform for a lot of players I think.