Overview
SOME SPOILERS ARE PRESENT IN THIS BUILD GUIDE.
Light Machine Guns are a fun new weapon available in Heavy Duty. They hit hard but can only make burst attacks and expend a lot of ammunition in the process. The new feat suite allows for a very heavy style of play, allowing you to forgo mobility and take the fight to your enemies head on. While they are many viable ways to build these weapons, this build will focus on letting you maximise your crafting potential to create powerful weapons earlier. This build was successful on Dominating difficulty with Oddity experience.
I was beta testing the Expeditionless install case, so this guide is designed to let you beat Tchort at L25 without Expedition installed. However, the build will be significantly better if you add specializations and the veteran feats.
The strategy section isn't going to go over every encounter because there are too many and the usual advice applies. Remember your move+shoot penalty, lighting, and occassionally deploy bear traps and use your grenades + drugs.
This build guide could potentially support adding miniguns in, but I found them a little weak in the current patch (1.2.0.9) and thus I won't talk about them.
Ability Scores
Strength - 10
Dexterity - 3
Agility - 3
Constitution - 6
Perception - 8
Will - 3
Intelligence - 7
Ability Score Progression - Put your first point at L4 into Strength. Put four other points into Constitution, and one point into Perception.
Skills
Heavy Guns - Max this at all opportunities.
Throwing - I invested 67 points to get to 60 effective. You will want to chuck crap grenades to potentially finish off enemies that you don't want to waste ammo on, or to sometimes use AP efficiently, especially when you want to move in the same turn. I did this quite late, but you should find windows to add points as you see fit.
Hacking - Should end at 94 spent (130 effective). Comes with experience, but you want to stick roughly at the synergy limit for each level.
Lockpicking - Should try to get to 130 effective. Since this is Dex and synergizes with Mechanics, you should expect to spend about 120 points. (Jackknife et al will do the rest).
Mechanics - Max this at all opportunities.
Electronics - Max this at all opportunities.
Biology - Get enough to craft Supersoldier Drug. (130 effective).
Chemistry - Get enough to craft Gas Grenades early. Hold off on adding more points till Mercantile skill is finished. After that, grab chemistry so you can make Napalm Grenades + W2C rounds + Incendiary Ammo (60 effective). At the end of this build, you will have enough spare points to craft Mark V grenades if you'd like, but they are not required to finish the game.
Tailoring - Max this at all opportunities.
Mercantile - Max until you hit 70 base points. With a Large Waist Pack + Under Pie you will be able to unlock Efreitor Hanna's extended inventory.
Feats
1 - Expertise
1 - Conditioning
2 - Disassemble (This is early due to my personal preferences, you can rearrange this with Suppressive Fire or even take it much later. It's up to you.)
4 - Brute Aim
6 - Full-Auto
8 - Suppressive Fire
10 - Concentrated Fire
12 - Heavy Metal
14 - Mag-Dump
Good Choices for Later Feats In No Particular Order:
Gun Nut - More damage.
Opportunist - More damage. Always triggers because of suppressive fire.
Juggernaut - You will be playing heavy armor due to Heavy Metal, so this will give you even more survivability.
Last Stand - Powerful; many hard encounters can be won thanks to an extra turn of life.
Pack Rathound - Even with 11 Strength, you will want to bring a ton of ammo to Deep Caverns. Did not regret this choice.
Doctor/Fast Metabolism - CON builds appreciate more healing.
Nimble - Didn't try this, but apparently this doesn't conflict with Heavy Metal.
Early Game Strategy
The early game in this build is very rough. At first, you will rely on the 75% Heavy Guns synergy points for your gun skill plus a few small points of Expertise (which isn't doing too much except just making the kills a bit more reliable). You may get lucky and find an early LMG frame but I wouldn't bank on it. LMGs are also very expensive to create in the very early game. Given that you are only at 8 Perception, this means that your guns should be barely capable enough on Dominating. You should have no issue with the early encounters as long as you're using all the fence tricks, flares and other ways of dealing with Rathounds efficiently.
The first major barrier will be the Azuridae when you're trying to save Newton. For this, I spent money and used a lot of incendiary grenades. Totally worth it, as this is probably one of the hard points in the run and it'll get easier later.
The SGS compound is also going to be a little tricky. You can pick up some strong early game armor by either getting the soldier at the GMS Compound killed by the Rathounds, or fighting one of the Lurkers in the Under Passages (one of them has a very powerful tactical vest).
Rathounds can be cheesed with flares and the use of your allies. The bots are worth spending EMP greandes and 5mm W2C ammo on, because you won't care about these later. Most of the raider fights at the end are technically skippable, but you will be able to hack the sentry turret and can probably kill the leader with some well placed bear traps/caltrops.
Once you get to Junkyard, you should try to craft an LMG and some Night-Vision Goggles. The Ratchet is the preferred frame because it can be shot twice without the use of Adrenaline and has the highest rate-of-fire. If you're lucky you can get all the way up to 60 quality, which will be absolutely devestating. Make sure you look in all shops; and especially look out for the Ergonomic Frame + Compensator + Higher-Capacity Ammo Belt attachments. With just full-auto, you will be able to instantly kill the Plasma Walker in Elwood's house, and Depot A will not be too challenging as long as you don't get hit by Yells or can survive them out with fire grenades. You will spend a lot on ammunition, so expect to use Disassemble to convert sledgehammers into metal plates for bullet crafting, as well as selling what you can.
Mid Game Strategy
Levels 10-12 are where the build fully comes online. This is where the cap of your damage escalates tremendously. Most enemies in the game will be obliterated by your MGs as long as your hit chance is reasonable. Regularly upgrade when you find a better frame, and don't worry about using the best ammunition belts when you can, because you can always recover them with Disassemble. Carry around TNT so that you can craft bullets on the field when appropriate (you generate cases, and plenty of things disassemble into plates).
For most of the game, I crafted a Regenerative Anti-Rifle Vest without Cloth. This is a good trade off between having a little bit of movement to adjust and use cover, but will protect you from most of the bullet-based enemies in the game.
Occasionally, mechanical armor isn't very useful in an encounter. Rathound Regalia was my go-to choice for most of these encounters, and it's super useful to have for the entirety of the game, but just remember the Heavy Metal feat will be reduced in power. Constitution makes psi enemies far less dangerous than for other builds. Carnifex was easy enough with Rathound Regalia preventing the damage debuff through sheer raw firepower.
In terms of good factions to side with, I sided with Praetorian Security for Chemhaze Grenades and potential selection of good frames + steel, and sided with the Protectorate to acquire gun oil for a bit of extra power.
Late Mid Game, once you get a good set of plates, I made the heaviest steel armor I could make with a Regenerative Vest combined with the heaviest Steel Boots. I am not going to be prescriptive about this, Steel is good enough for the entire game, but you can adjust the materials to whatever suits you. The Regenerative Vest will give you a lot of tankiness and is the best vest to use for the late game, but make sure you find a high quality one before you enter DC (~150 Q).
You will want a Large Waist Pack and Bullet Strap Belt for your two belt slot items (change as you need them).
For headgear, I used the Ironhead Mask while I lacked good shoes/plates, but then switched to having either NVG Crit Goggles (preferred), or anti-flashbang metal helmet.
Try to create a high-high energy shield with a powerful high efficiency energy converter, as this will be the best configuration to protect yourself from natural build counters (crossbows + sniper rifles).
Special bullet recipes are important to find. You will want to craft these bullets and save them for the later stages of the game. 8.6mm Incendiary Ammo for the Refurbished Brno will be especially excellent.
You'll also want a Galvanic Vest backup armor for fighting coil spiders.
Late Game Strategy (Heavy Duty + Deep Caverns)
With regards to the Heavy Duty side dungeon, I would first focus on extracting Gunslinger. Your build isn't great at keeping him alive and he'll get himself killed. You'd rather take a guaranteed 4 Oddity XP. You do not need to enter the main Compound grounds, just go to the side, grab the batteries, and come back to repair Marjorie. That will give you an option to track back through the tunnels.
Heavy Duty is a little easy to stealth through with 0 stealth points invested, so you can get to the Cognator without worrying about it with GS out of the equation. However, if you do fight, expect to be spending your resources; it is a good idea to build and use W2C ammo here. Remember not to throw grenades if there are cryobots protecting the troops.
You have enough PER to do the Fusion Cannon laser puzzle. The Fusion Cannon is excellent fun, and because you took the Disassemble perk, you can learn how it works and create a supercharged version of it. This is very fun, but a little impractical. Enjoy it, but I won't be using it for the run.
For your deep caverns preparation, you will be taking your important gear, ammo, spare TNT and a lot of guns. A LOT of ammo. Although there are stockpiles of varying rounds in the lockers in DC, I counted shooting ~1000 rounds in Mushroom Forest, ~1000 Rounds in Arke, and then you'll need to shoot more rounds in all the other sections. You do not need to bring repair kits, there'll be plenty of scrap to generate in DC.
I took the following guns into DC:
Refurbished MG3-42 for 7.62mm
Refurbished Brno for 8.6mm
Ergonomic Compensated Ratchet (~150Q) for 9mm
General Notes:
The Mushroom Forest will mostly be straightforward with MGs; you can't crit but you don't need them to kill the enemies. The one thing that will give you trouble are turrets. You may wish to switch up to a lighter armor so that you can move a bit more efficiently but just remember Heavy Metal's power will be reduced.
Tchortlings aren't much of a threat; MGs clear them no problem. However, use the proper game mechanics because you still don't want to fight these except when you have to. Get Echoing Soliloquay, use the hatches to escape the Eye of Tchort, etc.
Cuttlefish can be cleared with Incendiary Ammunition from the Brno.
When fighting Tchort, I did not need to do the mutagen puzzle at all. However, this is tricky and will need very precise play. You will need to make sure you have your NVGs fully charged, shield full, regen full and be stocked up on good ammo. Popping Aegis and Supersoldier drug early before combat will be useful. Your belt should be Napalm Grenades, Corrosive Acid Vials and Flashbangs.
Your focus is to move close to Tchort as quickly as possible. The ideal scenario is that you'll kill the first two tentacles as they spawn, which will let you escape combat twice and prevent you getting entangled. After that, you will be locked in as the Mouth of Tchort moves in. You will be ignoring all other enemies besides the Eye of Tchort however. As you are moving up to Tchort, you will toss a napalm grenade to shut off a few of the tentacles near Tchort (they don't attack while feared from burning). Make sure your shield is up.
Deploy adrenaline for the critical three turns at the end:
Turn 1 - You need to successfully hit with two Corrosive Acid vials (obtainable from Octavia or the worms in the Labyrinth in Deep Caverns). Spend the remaining 10 AP on Focus Stim.
Turn 2 + 3 - Unload onto Tchort's Eye with your LMGs. He should die on the third turn.
Conclusion
I will probably add some more commentary about this later, including more information about the refurbished LMGs and various frame differences and which are better. The new LMG weapons are very, very fun. Rewarding slow movement and careful consideration, this build really lets you play a style where you maximise the efficient use of your action points. The Tchort fight was especially thrilling; it's very technical and beating it at L25 without mutagen puzzle took the use of every piece of Underrail knowledge I had and didn't allow for mistakes. This build should be a lot easier to pilot if you have Expedition installed.
