Hot swap shotty instant reload spam
 Veteran Build - Warhammer 40k: Darktide 

Tested in h40. Sort of a mid range/close range build that does a lot of melee and plays up alongside the frontliner. Melee a lot and after melee kills you hot swap to shotgun to blast groups with infinite cleave damage + bleeds. The shotgun should be used to help speed up your horde clear, just manage your ammo based on need. You should be dumping heavier ammo into mixed hordes, and using your kraks to take out bulwarks, crushers, tightly packed maulers/armored ragers, and the occasional reaper or two. Also kraks are good to dump on bosses if you have them. 

Not meta, but viable in high tier content (havoc 40) if played well. Has limitations on deleting specialists at range quickly. You can swap the grenade to run smokes for team cover or frags for more control on groups. All 3 grenades work, kraks are nice when purple havoc modifier to help with purple bulwarks/crushers. Kraks also help with the build otherwise pretty meh boss dmg.  You can drop the 20% ogryn dmg node and even grenade tinkerer and flex pick a few different things. Some flex pick talent options: Extra ammo cap (I used to run it but found with proper ammo management its not really needed) Grenadier instead of tinkerer (if using frags), Opening Salvo isnt awful if you single kill reset swap the shotgun a lot, Exhilerating takedown can be ok for extra survivability, Serrated blade is good, especially with some different melees (like mercy killer knife), On Your Toes is pickable, Marksman, etc etc. I used to feel like the build needed One Motion, but once you get used to the slightly different swap and fire timing without it, its still very fast and you don't need it. I havent tested breakpoints, but it feels like Longshot more often results in more consistent kills without needing an extra shot on things such as snipers, trappers, bombers etc that are a bit further out from your normal range.