Mouse P.I. For Hire Guide: Building the Ultimate Arsenal
The ultimate breakdown of every weapon, schematic tier upgrade, and alt fire mode in Mouse P.I. For Hire.
Mouse P.I. For Hire packs a surprisingly deep arsenal for a noir rodent detective game. You start out with a basic pistol, but by the time you reach the endgame, you are clearing rooms with acid spewing shotguns and a literal cannonball launcher. The trick is knowing which weapons are actually worth your time and how they feel in a real firefight.
There are no secret vendors or hidden chests to hunt down here. Every single weapon unlocks naturally just by completing the main missions. Once the Schematics system opens up midway through the campaign, the real build crafting begins.
How Schematics and Upgrades Work
Once you unlock the Schematics system, you can start dumping resources into your favorite guns. Each weapon has three upgrade tiers, and every tier stacks improvements on top of the last one.
My biggest piece of advice? Pick two or three weapons that fit your playstyle and focus on maxing them out first. Spreading your Schematics across every single gun early in the game is a massive waste of resources. Also, keep in mind that the D Namite and the Hellrazor do not have upgrade tiers at all. What you see is what you get with those two.
The Complete Weapon Upgrade List
Here is exactly what every weapon does, what their alternate fire modes are, and what changes when you upgrade them.
| Weapon | Tier 1 Upgrades | Tier 2 Upgrades | Tier 3 Upgrades | Combat Role |
| Micer | Better damage, clip size, max ammo. Less spread and recoil. Alt Fire gives 3 quick accurate shots. | More damage, clip, max ammo. Less spread and recoil. | More damage, clip, max ammo. Less spread and recoil. | Medium range against smaller enemies. |
| Devarnisher | More projectiles, clip, max ammo. Less recoil. Alt Fire shoots a sticky acid blob with toxic area damage. | More projectiles, clip, max ammo. Less recoil. | More projectiles, clip, max ammo. Less recoil. | Sustained acid damage over time. |
| James Gun | Better damage, clip, max ammo. Less spread and recoil. Alt Fire is a rapid bullet dump with a wider spread. | More damage, clip, max ammo. Less spread and recoil. | More damage, clip, max ammo. Less spread and recoil. | Medium range crowd suppression. |
| Boomstick | More damage, pushback, max ammo. Less recoil. Bullets pierce 1 enemy. Alt Fire is a charged single shot. | More damage, pushback, max ammo. Clip is doubled. Pierces 2 enemies. | More damage, pushback, max ammo. Less recoil. Pierces 3 enemies. | Close range burst damage. |
| Portable Freezer | Bigger clip, max ammo. Faster freeze speed. Alt Fire is an exploding icicle that freezes an area. | Bigger clip, max ammo. Faster freeze speed. | Bigger clip, max ammo. Even faster freeze speed. | Slowing and freezing control. |
| Kiss Kiss | More max ammo, projectiles, pushback, burn damage. Less recoil. Alt Fire is a heavy explosive round. | More max ammo, projectiles, pushback, burn damage. | More max ammo, projectiles, pushback, burn damage. | Wave clearing with fire splash. |
| Jar Head | More damage, clip, max ammo, stun duration, projectile speed. Less recoil. Alt Fire is a concentrated beam. | More damage, clip, max ammo, stun duration, projectile speed. Less recoil. | More damage, clip, max ammo, stun duration, projectile speed. Less recoil. | Crowd control and stunning. |
| Loose Cannon | More damage, blast radius, pushback, max ammo. Less recoil. Alt Fire scatters cannonball fragments. | More damage, blast radius, pushback, max ammo. Less recoil. | More damage, blast radius, pushback, max ammo. Less recoil. | Explosive area damage and wall breaking. |
The Best Guns for Crowd Control
When you are completely surrounded, three guns stand out from the rest.
The Jar Head is your dedicated crowd control pick. It stuns normal enemies, and the Alt Fire laser absolutely melts targets if you aim directly for the head. Just remember that bosses are entirely immune to the stun effect, so swap it out before a major fight.
If you are still trying to figure out how to survive the early game and find those hidden upgrade materials, check out my complete walkthrough for The Vanishing Act right here.
The Kiss Kiss takes a different approach to crowds. It shoots explosive rounds that deal splash damage and set enemies on fire. Even if a goon survives the initial hit, they will keep taking burn damage. Finally, the James Gun is perfect for suppression. The Alt Fire dumps bullets so fast that it interrupts enemy attack patterns, completely stopping them from firing back at you.
Breaking Walls and Clearing Shields
You will frequently run into “totally normal walls” that hide secret areas, plus enemies carrying highly annoying shields. You need explosives to deal with both of these problems.
The Loose Cannon fires an exploding cannonball that wipes out groups and blasts open weak walls to reveal hidden loot. It is a fantastic weapon that only gets better as you upgrade it. The Alt Fire charges up and scatters shrapnel everywhere, making it great for grouped up enemies.
Your other option is D Namite. These throwable TNT sticks explode on impact, shredding shields and blowing open walls. Even though you cannot upgrade them, you should always keep a full stack in your inventory for emergencies.
Freezing and Melting Your Enemies
The Portable Freezer completely changes how you approach combat. Instead of dealing raw damage, it shoots a beam that progressively slows enemies down until they lock up completely in solid ice. Once they are frozen, you can just blast them with the Boomstick or the Loose Cannon without worrying about return fire. Upgrading this weapon makes that freeze effect happen significantly faster.
On the flip side, the Devarnisher is all about melting health bars. It shoots acid that eats away at enemies over time. It will not instantly delete a bad guy, but in longer, sustained fights, that toxic damage really adds up. Upgrading it simply means you shoot way more acid per trigger pull.
The Chainsaw Exception
We have to mention the Hellrazor. This is the only true melee weapon in the game. It is a literal chainsaw that will clear a room of basic enemies in seconds. It does not use the Schematics system at all, so you cannot upgrade it, but it honestly does not need it.
If you are hunting for more tips or just want to breeze through your backlog, check out my full collection of gaming guides right here. Need more help surviving Mouseburg? Check out our The Ultimate Mouse P.I. Beginner’s Guide for a complete breakdown of weapons, missions, and farming routes.
