Attachments can be gained by using Weapon Upgrade Kits; up to four can be attached to a single weapon.
Using a Weapon Upgrade Kit gives a choice of 3 or more randomly-selected Attachments for the currently equipped weapon, along with a small boost to its damage (+5%). Attachments with a gold color are rare attachments, which have a low chance to appear as an additional choice in the given selection.
15% chance to not consume ammo in the magazine. Scales with luck.
Increases the maximum amount of spare ammo by 40% and grants slightly faster ejection speed. Also increases ammo gain for the weapon by 20%.
Prints spare ammo (15% of magazine size rounded up) for every 50 heat generated. Production then consumes 10 heat. (Effectively, reduces heat generation by 20%.)
Losing shields (or health if no shield) grants ammo regeneration for a duration. Multiple instances can stack.
Bullets are directed towards the recoil center, increasing overall accuracy and precision. (Bullets have a high chance of choosing a more accurate trajectory)
Bullets always ricochet from surfaces or gain one additional bounce. Adds 10 armor penetration.
Adds an aiming laser. Grants movement stabilization and passively reduces weapon deviation.
Burst/Full-auto weapons: Turns the weapon semi-automatic and grants a +30% damage boost. Semi-Auto weapons: Turns the weapon fully automatic.
Adds full bullet enemy penetration or increases penetration damage. Increases bullet velocity.
Decreases damage by 5% if adding full penetration.
Increases damage to structures and props by 25% (includes turrets), and reduces enemy health regeneration by 50% on hits.
Last shot in the magazine deals increased damage and inflicts either stun or burn (for each projectile); damage scales with magazine size.
Increases damage by 15%, but also increases deviation by 3° and recoil by 10%.
Burst fire weapons: Fully removes burst delay. Semi/Full-Auto weapons: Increases firerate by 40%.
Power Link 4x4 Pin
Grants a random powerup for a few seconds on successful active reload.
Kills reduce running cooldowns for items by 1 second and decreases weapon deviation by 3°.
Upon ejecting a magazine, heat is set to minimum and unspent ammunition is always returned. Passively reduces heat generation by 15%.
Short Magazine Spring
Increases magazine capacity by 30%, rounded up. Magazines can only be ejected when completely empty.
Silver Bullet Alloy
Increases damage against Elite enemies and Bosses by 2% for each multiple of 100 of the player's maximum health, and bullets strip an additional plating from enemies.
Reduces recoil by 20% and deviation by 5° when standing still, but the effect is inactive while moving. Reduces recoil by 5% passively.
Significantly reduces deviation and recoil, improves recoil control and increases magazine by 15% rounded up at the cost of 10% damage.
Removes damage falloff over distance or increases distance damage increase. Increases maximum travel distance.
12% chance to fire an extra projectile with slightly increased deviation at no ammo cost.
Vital Data Collector
Every 4 kills grants +25 max health, until +400 max health has been gained. (64 kills.)
Heavily reduces movement speed penalty while firing, and reduces movement inaccuracy.
Ammo TP MkII
20% chance to not consume ammo in the magazine. Scales with luck.
Cranial Targeting CPU
Deal 100% increased headshot damage but lose 15% damage overall, powering the device costs 10 shields per shot. (Ingame tooltip is outdated)
Converts the weapon for run-and-gun use, strongly increasing deviation, movement stability, and damage. (+20% damage, +20% firerate, -30% recoil and +25-30° deviation.) Does not grant a movement speed buff.
Replaces vital weapon parts with a heavy Eternium metal mixture, strongly increasing weapon performance (+25% damage, +20% firerate, -10% recoil and -3° deviation) but reduces movement speed nearly to a halt when held.
Titanium Eternium Rifling
Decreases critical chance by 5% but increases critical damage by 75%.
Enemies killed whilst holding the weapon spawn red orbs that each grant 2 ammo directly to the non-empty magazine, 50 shield, and 5 heat.
Unlocks all ammo types for all weapons and allows switching of ammo types without ejecting first (only for the present weapon.). Switching ammo types generates 15 heat.
Super Heavy Compound
Bullets are extremely heavy, deal 50% more damage but slightly reduce movement speed and have 30% reduced range with strong damage falloff over distance. Effect is reduced but still noticeable with Titanium Rifling.
Decreases damage by 15%. Adds a new variant overtop the current one, and re-applies class bonuses.
40% chance to gain double ammo from pickups. Switches the weapon to a rapid fire 5-round burst, increases firerate by 25%. Burst weapons gain 3 extra shots per burst. Also reduces heat generation by 20%.
Kills grant permanent +0.25 luck, stacking up to 400 times. 5% chance to deal 200% damage, can crit.
decreases magazine size by 20%. Headshots return 1 ammo straight to the magazine.
Decreases firerate and damage by 20% but fires 2 additional pellets per shot, pulling from the magazine. Increases deviation by 30%, recoil by 10% and minimum heat by 10. Even if the magazine has fewer than 3 bullets, it will still fire 3 shots.
Gives a different bonus based on weapon type, these can stack if a weapon has multiple types (Example: Railgun is both a Marksman rifle and Special weapon.) See below for disambiguation.
Hot Swap currently unlocks all ammo types for both players in co-op. It is unknown whether or not this is a bug.
Twin Link increases weapon recoil by 5 when triggered, regardless of the weapon's individual values.
Twin Link will double pellet count for shotguns and weapons that shoot more than one projectile at once. This also goes for the Twin Link item.
Tri-Bolt-Carrier, however, will only add 2 projectiles per shot regardless of initial projectile count.
Caliber Reduction works by decreasing the overall damage by 10% while every attachment will increase it by 5% thus the reduction would be negated in 1 more upgrades.
Tri-Bolt-Carrier doesn't change the acid ammo pattern, meaning that you will have one projectile be acid in the following pattern:
The pattern pictured above: [normal | acid | normal | acid | acid] then repeat
Custom fitting specific bonuses:
Pistols: Halved recoil stat.
Shotguns: First shot in a magazine deals 25% more damage.
SMGs: Grants full armor penetration.
Marksman Rifles: Heavily reduces deviation and recoil.
Assault rifles: Increases headshot damage by 50%.
LMGs: Increases magazine size by 40%.
Special Weapons: Increases player movement speed by 50 while held.
The digital screen on the Digitalizer upgrade displays the word 'SHRIKE', the screen name of one of the developers.
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