In this guide I will look at every weapon in the game. First the raw data, then I will give advice based on the three different playstyles described in my guide to difficulty and classes.

Guide to Campaign Difficulty and Classes 

A Guide for Aliens: Dark Descent

By: RayThor

This guide is intended to help new players choose the best difficulty for their play style and tactical approach. The goal is to ensure a tense and enjoyable playthrough while avoiding too much frustration.

Weapons Categories
There are three categories of weapons.
A marine can only carry one of each category

• Primary Weapon
  
  • The main damage dealing weapon
    
  • Uses ammo clips to reload
    
  • Requires two uninjured hands to wield
• Secondary Weapon
  
  • The backup weapon
    
  • Does not require ammo clips to reload
    
  • Requires only one hand to wield
• Special Weapon
  
  • Activated via the skills bar
    
  • Does not require ammo clips
    
  • Costs 1 command point per use
    
  • Weapon is never in hands, needs to use half a second to switch weapons on every use

Weapon stats

• Damage per bullet
  
• Ammo per burst
  
  • The number of bullets fired per burst
• Burst duration
  
  • The time needed to fire a whole burst
• DPS
  
  • Calculated number for damage per second
• Magazine capacity
  
  • The number of bullets per ammo clip
• Reload duration
  
  • The time it takes to reload a weapon
• Dismemberment chance
  
  • The chance that a bullet dismembers an alien, losing an arm or leg
• Dismemberment chance per 5 second
  
  • Calculated chance that a bullet dismembers an alien, losing an arm or leg, per 5 seconds
• Associated skill
  
  • Skill usable while weapon is equipped

Standard Pulse Rifle
This is every marines starting weapon at level 1.

Weapon stats

• Damage per bullet
  
  • 1-2
• Ammo per burst
  
  • 2
• Burst duration
  
  • 0.75 seconds
• DPS
  
  • 4
• Magazine capacity
  
  • 100 bullets
• Reload duration
  
  • 3 seconds
• Dismemberment chance
  
  • 0.5 %
• Dismemberment chance per 5 seconds
  
  • 6.5 %
• Associated skill
  
  • UA1 Grenade Launcher
    
    • Used from the skills bar
      
    • Costs 1 command point per use
      
    • Area effect damage. Inner and outer area visualized by red inner area when targeting
      
    • Inner area damage is 10-20
      
    • Outer area damage is 6-10
      
    • Will interrupt most boss or miniboss special moves
      
    • Not allowed to fire if friendly targets are inside area of effect
      
    • Grenade has fast travel time

My opinion
Spamming grenades are the supreme dps of this game. When used in combination with the skill Suppressive Fire, it makes for excellent artillery on slowed approaching aliens. On my playthrough with only 2 marines in squad challenge I had my gunner take this weapon as his primary. Just to have the ability to use grenades. Now is this weapon for everyone all the time? Well, actually no. The grenade will not fire if your marines will be caught in the blast. This will cause frustration and lose valuable seconds thinking of a new solution. So for the Casual playstyle, having aliens in melee all the time, it is better to use a weapon with higher dps with just bullets. For the Experienced and Expert playstyles, at least one Standard Pulse Rifle should be taken to ensure the ability to launch grenades. When it comes to pairing with special weapons, try to avoid having the one marine with grenades use anything that takes time to switch weapons. A busy marine will not fire any grenades. Best paired with the sniper or mine.


Casual
No

Experienced
Yes, take 1

Expert
Yes, take 1

Smart Gun
Can only be used by the Gunner class. Will expand some stats with high level Gunner attributes.

Weapon stats

• Damage per bullet
  
  • 1-2
• Ammo per burst
  
  • 4
    
  • Level 10 Gunner gets up to 100 % increased rate of fire with stress step 3.
    
    • 5-8
• Burst duration
  
  • 1 second
• DPS
  
  • 6
    
  • Level 10 Gunner gets up to 100 % increased rate of fire with stress step 3
    
    • 8-12
• Magazine capacity
  
  • 150 bullets
• Reload duration
  
  • 5 seconds
• Dismemberment chance
  
  • 0.3 %
    
  • Level 6 Gunner gets 1 point increase from class attribute
    
    • 1.3 %
• Dismemberment chance per 5 seconds
  
  • 5.8 %
    
  • Level 6 Gunner gets 1 point increase from class attribute
    
    • 23.0 %
      
    • Level 10 Gunner gets up to 100 % increased rate of fire with stress step 3
      
      • 40.8 %
  • Associated skill
    
    • M56 ACT - Gunner Upgrade
      
      • Allows the Gunner to deploy the Smart Gun as a sentry turret
        
      • The Gunner will use his secondary weapon while the Smart Gun is deployed
  My opinion
  This weapon is by far the highest pure dps weapon in the game. And when combined with the Gunners class attribute, Unleash Hell, it doubles that high dps. To get the most out of this weapon means mastering stress and traumas, is for the Expert playstyle only. But even without boosting dps with stress, this weapon is the best for every playstyle. As for the M56 ACT upgrade, I think it is an upgrade that does not fit into any playstyle, skip. Remember that the highest dps marine should never do anything else in a fight than press the trigger, this means it should always carry the mines.
  
  Casual
  Yes
  
  Experienced
  Yes
  
  Expert
  Yes
  
  
  

Heavy Pulse Rifle
Requires a level 6 marine

Weapon stats

• Damage per bullet
  
  • 1-2
• Ammo per burst
  
  • 3
• Burst duration
  
  • 1 second
• DPS
  
  • 4.5
• Magazine capacity
  
  • 125 bullets
• Reload duration
  
  • 4 seconds
• Dismemberment chance
  
  • 0.6 %
• Dismemberment chance per 5 seconds
  
  • 8.6 %
• Associated skill
  
  • None

My opinion
Now things get interesting. The Heavy Pulse Rifle is an upgrade in dps compared to the Standard Pulse Rifle. It loses the grenade launcher, so keep that in mind. Every playstyle should get this rifle as soon as a marine gets to level 6. Materials should never be a problem unless you refuse to skip days early in the campaign. When we get to endgame considerations and compare this rifle to the Plasma Rifle, then for some playstyles and corresponding difficulty settings, it becomes more complex. In general the less hitpoints an alien has, the more useless the crit profile of the weapon becomes. And the more damage an alien does, especially if playing on +5 alien damage, the more dangerous it is to let an alien get close. And finally the longer a fight takes, the more weight is given to the pure dps of the weapon. Consider open spaces and sustained fights like defence events to be in favour of the Plasma Rifle just for the increased raw dps. But in closed spaces and surprise attacks, on max alien hitpoints, the Heavy Pulse Rifle is better. If not playing on increased alien damage, then always pick Plasma Rifle.

Casual
Yes, until you can take Plasma Rifle

Experienced
Yes, until you can take Plasma Rifle

Expert
Depends on alien damage setting and mission to choose instead of Plasma Rifle

Plasma Rifle
Requires a level 10 marine

Weapon stats

• Damage per bullet
  
  • 2-3
• Ammo per burst
  
  • 2
• Burst duration
  
  • 1 second
• DPS
  
  • 5
• Magazine capacity
  
  • 100 bullets
• Reload duration
  
  • 3 seconds
• Dismemberment chance
  
  • 0.5 %
• Dismemberment chance per 5 seconds
  
  • 4.9 %
• Associated skill
  
  • Overloaded Plasma Beam
    
    • 2-3 damage per 0.1 seconds of beaming in the beam area
      
    • Takes 1 second to charge beam before it fires
      
    • The marine can move while beaming
      
    • Beam duration is about 2-3 seconds
      
    • Total beam damage is about 63 on average
      
    • The beam stuns aliens
      
    • The beam does not create noise.
      
    • Can stealth kill eggs, roaming aliens and humans, but it is a risk of detection on sleeping aliens
      
    • The marine must use secondary weapon while the Plasma Rifle cools down
      
    • Bug chance. The marine may get stuck in slow walk mode
      
    • Bug chance. The marine may stop responding to orders
      
    • Bug workaround: After using beam, the marine must not interact until after cooldown

My opinion
Since the Plasma Rifle has a level 10 requirement it is only available at the later stages of the campaign. One reason to start a NG+ campaign is to get this rifle early. The Plasma Rifle is only second to the Smart Gun in terms of dps. For most player styles it is the natural rifle to end up with, but as explained on the Heavy Pulse Rifle, there exists some cases where a higher crit profile is preferred. For the Casual playstyle this weapon should be on every marine except the gunners. For the Experienced playstyle one Standard Pulse Rifle should be taken besides the Smart Guns on the gunners. For the Expert playstyle at least one Plasma Rifle should be taken for the ability to stealth kill.

Casual
Yes, except bring Smart Guns for the gunners

Experienced
Yes, except bring 1 Standard Pulse Rifle and Smart Guns for the gunners

Expert
Yes, bring at least one for the beam

Service Pistol
This is every marines starting weapon at level 1.

Weapon stats

• Damage per bullet
  
  • 1
• Ammo per burst
  
  • 1
• Burst duration
  
  • 0.5 seconds
• DPS
  
  • 2
• Magazine capacity
  
  • 12 bullets
• Reload duration
  
  • 1.5 seconds
• Dismemberment chance
  
  • 0.25 %
• Dismemberment chance per 5 seconds
  
  • 2.5 %
• Associated skill
  
  • None

My opinion
Decent weapon on lowest alien hitpoint settings (10 hitpoints).
As with all secondary weapons, they are only used when you run out of ammo or having your hands unavailable by some other reason. There is no reason to use this when Revolver or SMG becomes available.

Casual
Upgrade to Revolver or SMG when they get available

Experienced
Upgrade to Revolver or SMG when they get available

Expert
Upgrade to Revolver or SMG when they get available

Revolver
Requires a level 3 marine

Weapon stats

• Damage per bullet
  
  • 1-3
• Ammo per burst
  
  • 1
• Burst duration
  
  • 0.75 seconds
• DPS
  
  • 2.7
• Magazine capacity
  
  • 6 bullets
• Reload duration
  
  • 1.5 seconds
• Dismemberment chance
  
  • 0.9 %
• Dismemberment chance per 5 seconds
  
  • 5.3 %
• Associated skill
  
  • None

My opinion
As with all secondary weapons, they are only used when you run out of ammo or having your hands unavailable by some other reason. There is no reason to use this when SMG becomes available.

Casual
Upgrade to SMG when it gets available

Experienced
Upgrade to SMG when it gets available

Expert
Upgrade to SMG when it gets available

Submachine Gun
Requires a level 6 marine

Weapon stats

• Damage per bullet
  
  • 1
• Ammo per burst
  
  • 2
• Burst duration
  
  • 0.6 seconds
• DPS
  
  • 3.3
• Magazine capacity
  
  • 48 bullets
• Reload duration
  
  • 2 seconds
• Dismemberment chance
  
  • 0.25 %
• Dismemberment chance per 5 seconds
  
  • 4.1 %
• Associated skill
  
  • None

My opinion
As with all secondary weapons, they are only used when you run out of ammo or having your hands unavailable by some other reason. The SMG is the only secondary weapon that can use the skill Suppressive Fire.

Casual
Yes

Experienced
Yes

Expert
Yes

Shotgun
This is every marines starting weapon at level 1.

Weapon stats

• Damage
  
  • Short Range (0-6m)
    
    • 10-20
  • Medium Range (6-12m)
    
    • 5-10
• Dismemberment chance
  
  • Short Range (0-6m)
    
    • 30 %
  • Medium Range (6-12m)
    
    • 15 %
• Stun effect?
  
  • Yes, 1 second
• Associated skill
  
  • Shotgun Blast

My opinion
On lower alien hitpoints settings Shotgun instakills aliens. Aliens often try to dodge and jump sideways to avoid being hit. The blast cone is very narrow and easy to dodge. If playing on +5 alien damage, then you need nerves of steel to rely on the shotgun. That being said it is useful to have a shotgun available if one of your marines is on the ground wrestling with an alien, as the shotgun allows shooting through a melee without hitting friendlies. And the stun effect also interrupts minibosses special effects. For the Casual and Experienced playstyle Shotgun is a must. The Expert playstyle may consider spamming grenades instead, keeping the killing a bit further away from the squad. Shotgun is the solution to a bad situation. How often does that happen to you? I get hit by aliens about 1-2 times total in a campaign. But nice to have for those situations.

Update:
The stun effect has no travel time.
So if a marine at maximim shotgun range shoots at an alien, then the alien will get stunned instantly when the shot goes off, while the pellets have travel time and will do damage when they arrive at the target. This makes the shotgun quite better and suitable for just rushing through aliens while shooting.

Casual
Yes, take it on at least 3 marines

Experienced
Yes

Expert
Take one for show

Flamethrower
Requires a level 2 marine

Weapon stats

• Range
  
  • 5-15m
• Damage
  
  • 5-10 per second
• Enemy burning duration
  
  • 4 seconds
• Total damage on burning enemy
  
  • 20-40
• Burst duration
  
  • 3 seconds
• Area burning duration
  
  • 30 seconds
• Stun effect?
  
  • No
• Associated skill
  
  • Incineration

My opinion
Easily the best weapon in the whole game. As long as there exists another path from the aliens to your marines, the aliens will choose to path around the flames to not get hurt. This is an excellent tool to use on those many scripted events where aliens come at you from all directions. It is possible to funnel the aliens to come at you from only one direction. The trick is to never fully block the way but to leave a chokepoint open. It is not allowed for your marines to enter the flames, so keep in mind not to block off your squads movement. When it comes to the pure damage, it is super good on low alien hitpoints setting, but drops in usefulness with higher alien hitpoints. Also the marine using the Flamethrower stands still for 3 seconds, could be dangerous when speed is of the essence. I think every playstyle should carry 1 flamethrower.
Bug: When flaming alien eggs and then exiting the room and reentering the eggs will be alive as some kind of unkillable ghost eggs. Reloading the map by going up and down an elevator will fix this.

Casual
Yes

Experienced
Yes

Expert
Yes

Mine
Requires a level 2 marine

Weapon stats

• Activation radius
  
  • 2.5m
• Damage
  
  • Inner Blast(0-3m)
    
    • 20-35
  • Outer Blast(3-6m)
    
    • 15-30
• Dismemberment chance
  
  • Inner Blast(0-3m)
    
    • 50 %
  • Outer Blast(3-6m)
    
    • 50 %
• Placement time
  
  • 4 seconds
• Stun effect?
  
  • Yes, 1 second
• Max deployed mines
  
  • Unknown. I must have deployed close to a hundred mines on a mission
• Associated skill
  
  • Mine

My opinion
Mines are the command point rich players dream tool. On lower alien hitpoints settings it will always kill a standard alien, but on highest setting it usually takes two mines to kill an alien. I had fun with mines on my playthrough with 11 command points max and 10 seconds to regen another. Since it takes 4 seconds to deploy a mine, it was a challenge to run out of command points. If you know the maps, it is possible to plant mines before scripted events to make everything a cakewalk. But it requires a lot of command points, so will not fit into every playstyle. For the Casual playstyle I would suggest skipping mines altogether. The Experienced playstyle should consider bringing mines if they can afford it command points wise. The Expert playstyle should always bring at least one marine with mines. Bringing two marines with mines speeds up deployment, useful if two mines are needed to kill. Also keep in mind not to deploy any motion trackers or sentry guns inside the blast area of the mines, as this will keep the mines from detonating. This also goes for your marines, if they are even slightly inside the blast area, no explosion will happen.

Casual
Skip

Experienced
Yes, if you can afford the command points

Expert
Yes

RPG Launcher
Requires a level 6 marine

Weapon stats

• Range
  
  • 45m
• Damage
  
  • Inner Blast(0-1m)
    
    • 80-120
  • Outer Blast(1-2m)
    
    • 20-30
• Dismemberment chance
  
  • Inner Blast(0-1m)
    
    • 1 %
  • Outer Blast(1-2m)
    
    • 1 %
• Fire delay
  
  • 1 second
• Stun effect?
  
  • Yes, 1 second
• Associated skill
  
  • RPG Launcher

My opinion
The RPG is really not needed for any playstyle. It has huge damage, but for most playstyles alien hitpoints are too low to justify bringing it along. There is also the handling problem of not being able to target the ground, the rocket will just continue onwards until it reaches a wall or max range. Also the area effect radius is very small, and will really not do any damage if not a direct hit. It is best used as a follow up weapon after stunning the boss with something first. For the Casual and Experienced playstyles, the alien hitpoints are way too low, and they should consider skipping this. The Expert playstyle may find a use for it depending on squad composition. When I did a No Sniper Challenge playthrough I found that the RPG could achive some of the same results as the sniper. Considering a direct hit on a roaming alien, it will not send any message back to its hive as it is already dead. Likewise sleeping aliens can be killed by the RPG as long as there are no other aliens in view or in the same room. And finally it is also excellent to divert noise attention, as the aliens will run to the place of the explosion. In the end I mostly bring the RPG because I have nothing better to bring. For fun.

Casual
Not needed. Bring it for fun.

Experienced
Not Needed. Bring it for fun.

Expert
Not Needed. Bring it for fun.

Sniper Rifle
Can only be used by the Recon class.

Weapon stats

• Range
  
  • 80m
• Damage
  
  • 42
• Targeting time
  
  • 1 second
• Stun effect?
  
  • Yes, 1 second
• Associated skill
  
  • Precision Shot

My opinion
A game changer. The king of stealth weapons. Not to be used without the Silencer upgrade on the Recon, unless you feel in need of some action. (The sound of the shot moves faster than the bullet) The high damage is enough kill every normal alien with one shot without being detected. The marine will stand still for the duration of the shot, this usually makes sniping in combat tricky, easily interrupted if hit. The Recon needs a clear line of sight to the target. This can be somewhat tricky as default movement is with the whole squad. I usually pause the game before ordering the squad to move. Then select the other marines one by one and order each one to stop until only the Recon is moving. This will enable the Recon to enter rooms first. Another way is to stand close to the door, then order the squad to move away and then select the Recon and order it to stop. This will seperate the Recon from the rest. Then move into the room, and as the Recon now is closest, it will enter first. Another nice thing is the stun effect on the Sniper Rifle, excellent for halting bosses and buying some time. Due to the tricky movement and stealth mechanics of the Sniper Rifle, I think this is best suited for a patient playstyle focused on stealth. As such the Casual playstyle should consider dropping it altogether. The Experienced and Expert playstyle should always bring 1 Sniper Rifle.
Bug: When sniping alien eggs and then exiting the room and reentering, the eggs will be alive as some kind of unkillable ghost eggs. Reloading the map by going up and down an elevator will fix this.

Casual
Skip it

Experienced
Yes

Expert
Yes

Deployable Sentry Gun
Costs 1 tool to repair.
Costs 1 ammo clip to reload.
Did some testing.

Weapon stats

• Hitpoints
  
  • 4
• Damage per bullet
  
  • 1-3
• Ammo per burst
  
  • 6
• Burst duration
  
  • 1 second
• DPS
  
  • 12
• Accuracy
  
  • Unknown. Observed 6 out of 10 shots hit. EDIT: 75% is in the game files.
• Magazine capacity
  
  • 250 bullets
• Placement time
  
  • 5 seconds
• Reload duration
  
  • 7 seconds
• Dismemberment chance
  
  • Unknown
• Dismemberment chance per 5 seconds
  
  • Unknown
• Associated skill
  
  • Sentry Gun
    

My opinion
When you put down 4-5 of these beasts, then nothing can touch you.
Should always be placed in the back farthest away, so they do not get destroyed.
Every playstyle should carry as many as possible at all times.

Casual
Yes

Experienced
Yes

Expert
Yes

Having looked at all the weapons, I will now give an example loadout for every playstyle.

Casual

• Sergeant - Plasma Rifle - Shotgun
  
• Gunner - Smart Gun - Flamethrower
  
• Gunner - Smart Gun - Shotgun
  
• Medic - Plasma Rifle - Shotgun
  
• Gunner - Smart Gun - Shotgun/RPG

Experienced

• Sergeant - Plasma Rifle - Flamethrower
  
• Gunner - Smart Gun - Mine
  
• Recon - Standard Pulse Rifle - Sniper Rifle
  
• Medic - Plasma Rifle - Shotgun
  
• Tecker - Plasma Rifle - Shotgun/RPG

Expert

• Sergeant - Plasma Rifle - Flamethrower
  
• Sergeant - Plasma Rifle/Heavy Pulse Rifle - Shotgun
  
• Gunner - Smart Gun - Mine
  
• Recon - Standard Pulse Rifle - Sniper Rifle
  
• Sergeant - Plasma Rifle/Heavy Pulse Rifle - Mine/RPG

Happy Gaming!