Anti-Elite Support Bolter - Havoc 40
 Veteran Build - Warhammer 40k: Darktide 

Designed around hitting breakpoints on elites in high havocs. The build's major deviation from meta Focus Target! talent setups is investing in Kill Zone on the lower left side of the tree for more reliable breakpoints.

The combination of 6 stacks of Redirect Fire! , some Focus Target! , Pinning Fire and Skirmisher stacks, Longshot , and Kill Zone end up hitting a lot of one-shot breakpoints on ranged elites and specials without having to rely on crits. Reapers be two-shot on H39+ on weakspot hits without crits.

This build is inherently less versatile / has less solo-carry potential than dueling sword plasma meta builds, but provides exceptionally low TTK on priority targets and higher boss burst potential without sacrificing shout or focus fire. It fills a niche similar to Helbore builds, but with stronger defensive and burst characteristics.

Ranged Weapon

• Why Locke Mk IIb Spearhead Boltgun over Locke Mk III Spearhead Boltgun ? Ammo efficiency (more single-target damage per bullet and more ammo capacity), ability to burst bosses with weakspot hits in panics, and has cleave to kill snipers / bombers etc mixed into hordes (Mk III always detonates on the first target hit, even with Withering Fire ). The Mk III is superior for dealing with groups of regular shooters, but on balance I don't think it's worth it since if you have the rhythm of scope -> single-fire -> unscope before recoil fully registers -> re-scope you can get decent clearing capability without sacrificing the cleave needed to delete specials that can wipe a team.

• Why bolter over plasma? More ammo efficient if you hit headshots, much better ammo regen, lower TTK on particularly dangerous enemies like reapers without reliance on crits, a little more flexibility in situations involving surprise armor or bosses, lower TTK for shooter removal (higher ROF lets you retarget faster), better movement characteristics, equivalent or better capacity for burst damage and stagger in panic situations (tapping m1 to shred or stagger a rager/bruiser/mauler clump or instagib a reaper can save you, special action push can push bursters and stagger ragers on weakspot)

  - Notable weaknesses vs plasma - reduced cleave / no wallbangs, cannot stagger muties/crushers/captains with headshots.

• Why bolter over Helbore? More capacity to quickly burst or solo bosses in emergencies, equivalent or better cleave, less reliance on crits for hitting breakpoints (can more easily justify keep a health or third toughness curio instead of a stamina curio), better performance in panic situations

  - Weaknesses vs Helbore - much less ammo efficient, no huge instant brittleness team utility from Armourbane , no bayonet for captain shields, worse performance against crushers and maulers

Bolter Blessings

• Pinning Fire will almost always have at least 2 stacks and often the max 5 due to sheer density of enemies. Essential for breakpoints once specials and elites reach their maximum health bonuses from havoc modifiers (on levels 38 and 39 respectively). 
  • Note that stacks of Pinning Fire and Focus Target! each effectively add 5% damage , so you can calculate breakpoints with them interchangeably. E.g. shooting a bolter with 5 stacks of PF at an untagged enemy is equivalent to shooting with 3 stacks of PF at an elite tagged with 2 FT stacks.
• Puncture helps with ammo efficiency if you're just short of a breakpoint due to missing a stack somewhere and provides useful supplemental DoT against thick targets like bosses. Helps reduce cognitive overhead and retarget faster.
• Surgical helps with breakpoints against reapers on Havoc 39+ if you don't have lots of FT/PF/Skrimsher stacks built up. At mid range you'll want two weakspots with at least one crit unless you have 3+ PF/FT stacks. Crits also give you a bit more room to bodyshot softer enemies like scab gunners and specials and guarantee weakspot kills on flamers without needing favorable PF/FT/Skirmisher stacks.
  • Choice between Surgical and Puncture is up to personal preference. If you're confident in your ability to hit weakspots and keep PF/FT/Skirmisher stacks up, take Puncture since it'll let you retarget faster - don't need to wait for crit chance to tick up before firing. 
  • Has excellent synergy with Deadshot if you choose to take that talent, though
• Shattering Impact is generally not worth it since you're trying to one or two-shot your primary targets. Builds like Rumbler Ogryn and arc Skitarii apply brittleness much more effectively. Kraks are generally the better option for armor packs if you're playing into rotten armor, and your melee should be able to handle isolated armor. For unyielding bosses a power or dueling sword will apply damage much more efficiently

Bolter Perks

• +Unyielding is effectively required for hitting two-shot breakpoints on Reapers on Havoc 39+
• +Elites and +Flak is a tossup. 
  • +Elites helps with more reliable reaper two-shots on H39+ - with 3 FT/PF stacks, two non-crit weakspots is enough. Extra damage on ragers and plasma gunner headshots is also welcome (flak bodyshots are lower ttk, but sometimes you can only see their heads over hordes)
  • +Flak helps killing scab gunners. With +Elites, you need ~3 total stacks of FT/PF to kill on H39+ with a non-crit weakspot. 
  • I prefer +Elites because scab gunners are usually positioned in groups, so it's easier to build PF stacks by shooting at them and facilitate easier one-shots in the event you miss one. Reapers won't get staggered by bolter headshots, and shooting up at their heads doesn't stagger as many nearby enemies as shooting into a horde, so you won't get as much free damage on subsequent shots.
• Sub H39, +Unyielding doesn't change breakpoints on reapers much - with or without, they're two-shot headshots (or one headshot one bodyshot with some PF/FT stacks). +Flak and +Elite works fine there.
• If team lacks answers for quickly deleting twins, can take +Carapace to allow for one-phasing Rinda. Otherwise not as useful as other choices - helps if you need to panic clear some crushers or maulers, but kraks are generally better suited for armor packs if you have them. With plasma gunner and mauler headshots you'll get equivalent TTK by hitting flak bodyshots and for scab ragers you should always be going for headshots

Blitz and Talents

• All of vet's grenades are fantastic and you can pick whatever works best with your comp. 
  • Smokes provide the greatest unique utility - turning off shooters, and making Rodin Karnak run around in circles / not throw tox mines if he's stuck in smoke.
  • Taking Krak Grenade enhanced with Grenade Tinkerer lets you preserve your bolter ammo for elites/specials. Use grenades liberally against armor packs and bosses. 
  • Frags are excellent but I tend not to take them since I feel like I'm wasting them if I'm not throwing them all the time, and even with One Motion I like to keep my bolter out as much as possible for dealing with threats at range to minimize time where I can't shoot stuff.
• Essential talents for ranged breakpoints: Focused Fire for 6 Redirect Fire! stacks, Kill Zone , Superiority Complex, Precision Strikes , Bring it Down! 
  • Skirmisher not 100% necessary but provides huge utility and is the single biggest melee damage boost this build can get.
• Volley Adept is basically required for Bolter - it's the single biggest reload buff you can get and you'll have 95%+ uptime. Further reload nodes or a +reload perk on the bolter aren't worth it imo. Just practice cancelling the reload animation right when the final sound cue starts when pulling back the slide (to see exactly when, watch when your ammo counter changes from 0 to 15) - cancelling with a sprint is fastest, but the push special action is only a tiny bit slower than a sprint cancel and you can do it while dodging. You can buffer ADS out of special action, too.
• Born Leader is the best way in the tree to reach Kill Zone imo. Fully Loaded isn't required for Bolter (see appendix), and Born Leader has higher uptime than Competitive Urge. Good synergy with Ogryns to keep their huge toughness pools topped up.
• Flex nodes
  • Exhilarating Takedown can provide a ton of TDR and typically has 40%+ total combat uptime with more than one stack since you'll be aiming for weakspots on crucial targets. IMO a better pick for TDR than the 10% TDR gray node. ET has good synergy with Born Leader, too. Not strictly necessary if you're confident in your evasion, though.
  • Leave No One Behind is helpful for filling gaps where Only In Death Does Duty End can't help (rescuing from ledges, traps, rescues, etc.) but can be swapped for Desperado  at no cost if you want to increase melee damage output. Desperado is particularly helpful if you elect to take a melee weapon other than the power sword.
  • Duck and Dive helps mitigate vet's reduced stamina pool relative to patches before 1.13.x and provides some a movement speed buff that is particularly welcome on the power sword. I find the node more reliable than Target Down! for regenerating stamina, which feels particularly important when paired with melee weapons with low stamina pools (e.g. dueling sword, tac axe) or get a ton of damage out of push attacks (e.g. power sword).
  • One Motion is theoretically optional if your awareness is cracked enough, but in practice it's very helpful since you'll want to have your melee weapon out for mobility most of the time, and that accelerated draw time will absolutely help you catch snipers and bombers. You can always shout to cancel the draw animation, but it's best to keep that capability for emergencies imo since instant gold health + kb + revive is a critical team resource.
• If you elect to pass on some of the above, decent candidates for replacement are: 
  • 15% melee damage boost
  • Agile Engagement 
  • Desperado 
  • Trench Fighter Drill
  • Target Down!
  • Rending Strikes 
    • Disproportionately benefits certain melee weapons like the shock maul.
  • Onslaught
    • Can be a poor man's Shattering Impact or Uncanny Strike, but should not be paired with them since they share the same brittleness cap
    • Pairs well with trench fighter drill on certain melee weapons
  • Deadshot (see critseeker section)

Melee Weapon

I recommend the Achlys Mk VI Power Sword with Slaughterer: It's the best way to kill chaff while keeping capacity to chunk armor and bosses.+Carapace will let you kill crushers and maulers quickly without spending resources, and will help you do meaningful damage to twins. +Unyielding is also helpful for bosses and bulwarks in particular. +2 Stamina is a good alternative perk if you elect not to take any stamina regen talents.

The average runspeed and dodge count, poor dodge distance, and vulnerability during the special activation (mitigated only by freezing stamina regen for sliding activations) make you less capable of clutching rescues or revives when shout is on cooldown relative to some other melee weapons, though.

Some other recommendations depending on team comp and personal preference:

• If team lacks a source of Skullcrusher  and/or very high single-hit damage to skip captain phases, you can take a Shock Maul. The special attack will chunk captain shields and make their fights go quicker. I prefer the Munitorum Mk III Shock Maul.
  • Extra dodge and block efficiency relative to powersword helps with survivability. Has the same runspeed, though.
  • +Maniac is non-negotiable (dreg ragers are your nemesis and muties take a couple of weakspot hits to kill). I usually run +Carapace as the second perk since cara damage is the weapon's biggest shortcoming.
  • Skullcrusher is probably the single best melee blessing in the game. The only reason not to take it is if your team has a Achlys Mk I Power Maul ogryn that's already applying skullcrusher to everything all the time, in which case you can take High Voltage
  • Hammerblow is my favorite blessing on the shock maul. It knocks back chaff and throws maulers on their ass, and staggers Crushers while at max stacks - staggering enemies with the maul applies electrocution debuff, meaning you can proc either Skullcrusher or High Voltage
  • Skullcrusher+High Voltage is okay but will suffer more in hordes since the maul's cleave isn't fantastic, and against crushers you'll have to use your special action if you want to stagger them and proc your blessings on your own.
  • Munitorum Mk III Shock Maul H1 -> L1 loop will keep you safe and prevent you from getting tripped by unkilled chaff
  • Stunning crushers and unshielded captains with special action is extremely funny but requires forethought and usually isn't worth it
  • Benefits from heavily from Rending Strikes (helps net damage against both carapace and maniacs), and the 15% melee damage boost node helps with chaff
• If you struggle to survive with powersword and want to prioritize mobility / staying alive and to better stall for shout revives, take a pokey dueling sword  - can't go wrong with Maccabian Mk IV Duelling Sword . 
  • Suggest taking Desperado (can swap for Leave No One Behind )
  • Suggest Thrust (for poking muties). Shred and Uncanny Strike are both good choices - I prefer the former for dealing with chaff, but the latter if the team lacks other brittleness sources or if playing into Rotten Armor.
  • +Carapace and +Unyielding for efficient armor removal and boss contribution. Substitute one of the perks with +Stamina if you skip stam regen talents.
  • Dump cleave damage for mobility
  • Rely on your movement attributes and parry to avoid getting bogged down. Getting isolated and bodyblocked by chaff is your biggest threat.

Tac Axes are a decent dueling sword sidegrade - being able to interrupt overheads and charging muties on special action weakspots is nice and the Atrox Mk VII Tactical Axe is comfier for horde-clear - but it'll struggle more with armor and can't contribute as well for bosses.

Power falchions are good all-rounders but do less damage to bosses compared to other options.

Synergies

• Works very well with anything that applies mass brittleness - e.g. Lorenz Mk VI Rumbler Ogryn with Shattering Impact , arc Skitarii with System Shock 
• Has exceptional synergy with other veterans - the Fire Team aura helps hit breakpoints even more comfortably / gives you more room to bodyshot. Plasma's biggest advantage relative to bolter is its increased cleave / greater reliability killing enemies in cover or behind walls, so having a plasma vet can plug holes in bolter's coverage.
• Horde-control specialists - e.g. Rifthaven Mk II Inferno Force Staff or Equinox Mk III Voidblast Force Staff or greatsword psykers, taunt ogryn, relic blade zealot etc - help keep space open for you to focus on distant threats.
• Works well with the Dog Whistle mod. I suggest auto-targeting: bombers, snipers, dreg/scab/plasma gunners, reapers, and Rinda Karnak / melee twin (tracking her quickly is hugely helpful). Flamers and trappers are okay to include but are usually easier to spot due to their aggressive movement. Set auto target cooldown minimum to 2 or 3 seconds to balance having healthy focus fire stacks and quickly identifying priority targets (setting the restriction by focus target stacks instead of by time exhibits some inconsistent behavior, esp when there are multiple focus target vets on a team). I also recommend having an easily accessible toggle bind for when you want to ensure you keep 6 stacks on a boss (I use the grave/tilde key).

Bonus Variation: Deadshot Critseeker / Helbore Cosplay

Less good than the prime build and imo essentially a goofy and suboptimal shout helbore build, but good fun.

Curios: Swap +health curio for +3 stamina curio. Swap +5% toughness on the curio for +5% health.

Talents: Swap Exhilarating Takedown or One Motion for Deadshot. Optionally swap another talent for Target Down! 

Bolter: Replace one of the blessings with Surgical (suggest keeping Pinning Fire)

Melee: Unchanged

Appendix

Bolter Ammo regen

• tl;dr - a lot will depend on Sharpshooter uptime, but Fully Loaded is very likely not necessary for a build running Survivalist. Sharpshooter will proc less often than Survivalist since the vet has to be the one getting the kill, so it won't be a 100% increase in regen compared to 1.12.x, but it should be more than the 25% loss from the node.
• Ammo capacities
  • Base reserve: 90
  • Fully Loaded (FL) reserve: 112
• Auras 
  • Sharpshooter - 1% ammo on elite/special kill by vet, 5s CD
    • Base proc: 0.9 -> 1
    • FL proc: 1.12 -> 1. Recovers 2 every 9 cycles (remainder greater than 1 added to subsequent calculations)
  • Survivalist - 0.5% ammo on elite/special kill by anyone in coherency. 5s CD
    • Base proc: 0.45 -> 1. 
    • FL proc: 0.56 -> 1
• Pickups on H40
  • Tin: 6%
    • Base: 5.4 -> 6
    • FL: 6.72 -> 7
  • Stash: 20%
    • Base: 18.0
    • FL: 22.4 -> 23
  • Crate: 40%
    • Base: 36.0
    • FL: 44.8 -> 45