Callisto Protocol: Best Weapon Upgrades

The journey through Black Iron Prison is harsh and spending the the hard earned credits into the wrong upgrade can further fuel the nightmare.

Through the course of the game, you will come across different weapons in The Callisto Protocol, which largely works the same as the weapons in usual survival horror games but with an added twist. This unique twist makes them stand out but to realize their full potential, the weapons need to be upgraded first via credits. The credits in The Callisto Protocol are not easy to come by, which is why you should be careful with your weapon upgrade selection and only choose the best upgrades for each weapon.

Key Takeaways
  • There 7 obtainable weapons in The Callisto Protocol. Four of them are unlocked via story progression, while the rest are unlocked via schematics.
  • Every weapon has 3 tiers of upgrades, with each tier requiring a higher cost than the last. Additionally, some of the weapons feature alt-firing mods as an upgrade too.
  • The weapons are upgraded via credits which can be found by killing the enemies and opening boxes that are scattered all over the game.
  • The High Capacity Magazine & the alternate firing modes are one of the best upgrades in the game that is essential for pretty much every weapon in The Callisto Protocol.

Here’s a summary of every Best Weapon Upgrade in Callisto Protocol:

Weapon NameTypeUpgrades
Stun BatonMeleeRiot Control, Damage Upgrade 1 & 2, Block Break
BI-55 PistolSidearmStability Upgrade, High Capacity Magazine Upgrade, Magnum Rounds, Damage Upgrade, Swarming Rounds
GRP (Gravity Resistant Projector)Auxiliary RangedEnergy Upgrade (Small & Medium), GRP Velocity, Upgrade (Small & Medium), Recharge Speed Upgrade
Skunkworks Shotgun “Skunk Gun”SidearmHigh Capacity Magazine Upgrade, Magnum Rounds, Damage Upgrade, Swarming Rounds
Tk4 Riot Shotgun “Riot Gun”PrimaryHigh Capacity Magazine Upgrade, Magnum Rounds, Damage Upgrade, Explosive Rounds Upgrade
UJC Special OPS “Tactical Pistol”SidearmMagnum Rounds Damage Upgrade, TK33 “Burst Mod”:, High Capacity Magazine, Upgrade
UJC Special OPS “Assault Rifle”PrimaryMagnum Rounds Damage Upgrade, Stability Upgrade, TK63 “Homing Rounds”

Stun Baton

Melee Weapon
Upgrading the Stun Baton [Image by eXputer]
How to use your main melee weapon or Stun Baton is one of the first things The Callisto Protocol will teach you, as it will serve as the core and center of your combat encounters for the most part. So pouring your credits in Stun Baton will make the early-mid game encounters much more manageable.

Riot Control Upgrade

Kicking off our list is the Riot Control upgrade for the Stun Baton. This upgrade allows Jacob to perform a heavier swing that can send the enemies flying and even gives you the opportunity to score a couple of shots too, dismembering the enemy in the process. However, the attack has a long wind up, so make sure you have enough room to land the hit instead of pressing the button haphazardly in hopes of landing a hit.

Damage Upgrade 1 & 2

These 2 upgrades essentially do what it says on the paper, increasing the damage output of your normal and heavy attacks. This increased damage will not only make the late-game encounters more manageable but also will allow you to kill off some of the stronger enemies early on in the game much more easily.

Block Break Upgrade

Another great upgrade you can make to your arsenal is the Block Break. This upgrade allows you to break the arm of biophages if they try to interrupt your combo via blocking.

BI-55 Pistol “Hand Cannon”

BI-55 Pistol
Upgrading the Hand Cannon [Image by eXputer]
BI-55 Pistol is the first ranged weapon you will get access to in The Callisto Protocol. Its own damage is decent and is great for tearing off the limbs of some of the earlier game enemies, but the real highlight of this weapon is its alt fire mode, which makes this weapon an easy go-to choice even for the mid-late game encounters.

Stability Upgrade

The stability upgrade makes your aim steady, reducing the recoil from your shoots and allowing you to land follow-up shots much more accurately. For a game where every bullet counts, this upgrade is essential if you cannot handle the recoil and with how aggressive the enemies you would want those bullets actually to land on critical spots.

High Capacity Magazine Upgrade

If you stomp every enemy you kill and scavenge every resource you find, you will soon find your inventory full of bullets, but at the same time, wasting them still feels like a bad choice because you never know when these bullets can save your life. For this reason, we highly recommend installing the High Capacity Magazine, allowing you to load more bullets in your magazine and freeing up space for more items.

TK23 “Boom Bullets”

Boom Bullets is by far one of the best and most powerful upgrades of The Callisto Protocol. This upgrade basically gives you the ability to switch to an alternate firing mode which allows you to shoot bullets that cause a delayed explosion after landing. This is an extremely powerful upgrade, and the explosion from the bullets can bring even some of the scariest biophages to their knees.

GRP (Gravity Resistant Projector)

Gravity Restraint Projector
Upgrading the GRP [Image by eXputer]
GRP is a weapon that you will find fairly early on in the game, which basically gives you this telekinesis ability that allows you to pull in and throw away other objects or enemies. 

Energy Upgrade (Small & Medium)

For a tool that allows you to make enemies immobile for a moment and throw them around, it comes at a price. That price is its energy which depletes fast during encounters. With Energy Upgrades, you’ll be able to use GRP for far longer during the encounters.

GRP Velocity Upgrade (Small & Medium)

For some weird reason, the throws from your GRP don’t do any noticeable damage to your enemies, meaning the only advantage of your throws is to give Jacob some breathing room. In not every enemy encounter, you will find yourself surrounded by spiky walls and fast-moving fans, which lets you kill the biophages instantly. For this reason, we recommend buying the GRP Velocity upgrade that gives your throws the added damage bonus as well.

Recharge Speed Upgrade

The enemy encounters in The Callisto Protocol will likely consume all of your energy, leaving you will no GRP energy for further encounters, and if you don’t have any energy packs on you, then you are straight out of luck. Having this upgrade will recharge your GRP with time, and we highly recommend unlocking at least the small Recharge Speed upgrade to let the GRP automatically recharge as you further explore the Black Iron Prison and make your way toward the next encounter.

Skunkworks Shotgun “Skunk Gun”

Skunkworks Shotgun
Upgrading the Skunk Gun [Screenshot Grab: eXputer]
Skunk Gun serves the role of shotgun and is the first optional weapon you can acquire. It works the way most shotguns, but its great recoil control and decent short-ranged damage make it a great weapon for your journey through the Black Iron Prison.

High Capacity Magazine Upgrade

The biggest shortcoming of shotguns is their short magazine which forces the player to reload very frequently, and for a game like The Callisto Protocol, these reloads can result in your death as the enemies won’t gracefully let you reload your weapon. This is why High Capacity Magazine is an essential upgrade that lets you use this weapon in combat more effectively.

Magnum Rounds Damage Upgrade

Skunk Gun has decent damage, and bonus damage from Magnum Rounds Upgrade makes this weapon even better, especially for mid-late game encounters.

Swarming Rounds

This is an alternate firing mode that really sets Skunk Gun apart from any shotguns you might have seen. This mode allows Jacob to shoot swarming rounds at the enemies that pierce through their bodies and even rebound off the walls.

Tk4 Riot Shotgun “Riot Gun”

TK4 Riot Shotgun
Upgrading the Riot Gun [Screenshot Captured by eXputer]
Riot Gun is a two-handed pump-action shotgun that has an insane amount of close-range damage, plus it has a decent magazine that does not force you to reload frequently. Its alternate firing mode is capable of dealing extreme damage to enemies and kills off most of them in a single shot. The only drawback is that in its base form, it might not be that great considering the point in the story you receive this weapon, requiring you to pour some credits in it for upgrades from the get-go.

High Capacity Magazine Upgrade

The upgrade does what it says on paper and adds extra slots in your magazine in order to store more bullets making the weapon last longer during encounters without the need to reload.

Magnum Rounds Damage Upgrade

This upgrade raises the base damage of the Riot Gun, further easing the enemy encounters.

Explosive Rounds Upgrade

This upgrade is what truly this weapon is all about. Explosive Rounds turns Jacob into the boss himself by giving him the power to one-shot pretty much every enemy, minus the bosses and some of the larger, more fierce enemies. Even against the bosses, the weapon’s alternate firing mod proves to be extremely formidable and makes it a great choice if you are having difficulty facing one.

UJC Special OPS “Tactical Pistol”

UJC Special Ops "Tactical Pistol"
Upgrading the Tactical Pistol [Image Captured by eXputer]
The tactical pistol has a great recoil and fire rate but at the cost of low damage. It’s a weapon Jacob acquires very late into the game, and considering the difficulty of encounters, the damage isn’t enough to even with the increased fire rate. Additionally, some of your other weapons will already have great attachments attached to them, but if you somehow haven’t invested in them or are in a second playthrough, these are some of the best upgrades for Tactical Pistol in The Callisto Protocol.

Magnum Rounds Damage Upgrade

This upgrade is a no-brainer, as damage is the area Tactical Pistol lacks the most in. So it is highly recommended to get this weapon upgrade if you plan on using Tactical Pistol.

TK33 “Burst Mod”

This is an alternate firing mod that makes up for the Tactical Pistol’s low damage output. This mod fires ten rounds in a single burst which makes it great for targeting different areas of the biophages’ bodies.

High Capacity Magazine Upgrade

Normally you wouldn’t need this upgrade with this weapon, but it is essential if you plan on using the Tactical Pistol in burst mode. As mentioned above, Burst mode can consume 10 bullets in a single go, making the magazine upgrade absolutely essential.

UJC Special OPS “Assault Rifle”

UJC Special Ops "Assault Rifle"
Upgrading the Assault Rifle [Screenshot Captured by eXputer]
Assault Rifle is another weapon that you obtain very late into the game, and it suffers from the same issues as Tactical Pistol. As not an ideal weapon for that point in the game as you have much more powerful weapons already present under your belt by that point. It has a great fire rate and is excellent for stopping transformations but it doesn’t do well against groups.

Magnum Rounds Damage Upgrade

Assault Rifle, albeit having better damage than Tactical Pistol, still lacks in the damage department, which is why Magnum Rounds Damage is an essential upgrade for this weapon.

Stability Upgrade

Even with a good recoil, it is not uncommon to miss your shots with Assault Riffle, especially when firing fast-moving targets. That is where the added stability from this upgrade can help.

TK63 “Homing Rounds”

Homing Rounds is the alternate firing mod that automatically maneuvers itself in flight to hit moving targets. It’s not missile lock-on levels of tracking, and it’s just a mode that makes sure your shots land where they need to.


The Sci-Fi Survival Horror “The Callisto Protocol” is said to be a spiritual successor to Dead Space, but that’s only in its setting and atmosphere, as the core combat is much more brawler based than a shooter. And on how to adapt to this new playstyle, we highly recommend checking out our Callisto Protocol Tips & Tricks guide.

Akin to recent launches like A Plague Tale Requiem and Gotham Knights, The Callisto Protocol is plagued with performance issues, especially on the PC port, adding another nightmare of dealing with bad framerate on top of its own. However, tweaking the settings a bit can make the game playable if you desperately want to try it out now, and for that reason, we recommend going through our Callisto Protocol Best PC Settings guide.

This wraps up our guide on the best weapon upgrades for The Callisto Protocol. While most of the weapons can be obtained via story progression, some of the weapons are locked behind exploration/schematics, so make sure you search through every nook and cranny in order to not miss out on any of the weapons during your playthrough. For any questions, use the comment box below.

Next: The Callisto Protocol Review

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Abdul Haddi

Haddi is a Senior Writer & Editor at eXputer who loves to play games and talk about them like a fanatic. Hadi's years of experience in this industry let him provide a unique and critical perspective on games to share with his audience. His work is also featured on several other websites. You can hit him up in the comment sections or on his gaming network, and he’d love to respond to your queries about his content. Experience: 5+ years || Education: Bachelor's in Mass Communication || Previously Worked At Gamepur, Gear Siege, GearNuke || Written 300+ Articles || Covers Latest Game Guides

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