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Undyne777 - Cooleo

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About this mod

Overhauls the Vanilla firearm modification system by adding three (3) new modification categories: Fire Mode, Ammo Type, and Caliber. Vanilla & Far Harbor ballistic firearms supported!

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Firearm Modification Overhaul
Mod by Undyne777 & cooleo

Note from the authors, to anyone that still checks in on this regularly.

First, thank you to the FO4 Mod Community for your support on both this, and my other projects. I've dabbled in modding privately in past games, but this game has been my first foray on the scale that I have done. Your support and critiques kept me coming back and helped make this better (all 700+ endorsers, 13K+ downloaders, and 140+ comments).

Right now, due to work commitments and other personal developments, I am officially done with supporting this project. I don't have the bandwidth to do it justice. As of now (10/21/16), this project is 100% open-source to anyone who wants to take it and roll with it. Keep it going or change it up - that can be up to you. If you've enjoyed using this as much as I have, I hope you consider making it your own.

I've said it before and I'll say it again - BIG thank you to cooleo. He kept this thing going while I've been MIA. He pushed out a lot of refinements that I never thought of and for that we're all grateful. Can't wait to see what you crank out, dude!

Ever want an automatic .50 pistol that shoots plasma rounds?
5.56mm Hunting Rifle with cryo rounds?
5mm Submachine Gun with armor piercing rounds?
Well, this is the mod for you!


I started out modding Fallout 4 with a little project called Caliber Conversion Kit that sought to add multiple receiver options to swap out ammo types. Even after I completed that project and moved onto other things, I still felt like there was more to do in terms of overhauling the existing weapon mod framework. 

Thus, Gunsmith Extended was born. (NOT affiliated with the Weaponsmith Extended mod).

This mod does a deep dive series of changes to the existing modifications for ballistic firearms as pertains to receivers, fire modes, ammo types, and calibers. I drew on the things I learned working on my other mods to hopefully help diversify the options available when using vanilla weapons.

I hope you enjoy using it as much as I enjoyed making it! Cheers! :-)


Adds three (3) new modification categories to supported weapons at the workbench: Fire Mode, Ammo Type, and Caliber

e Mode: Switch supported firearms between automatic & semi-automatic. 'Nuff said.
Ammo Type: A cocktail of conventional and quirky ammo effects relevant to the Fallout universe
Caliber: Switch which type of ammunition your peacemaker uses! Stats will change relative to the type of bullet.

*Automatic Receiver changes: the existing "Automatic Receivers" have been converted to be "Light Bolt Receivers" that increase the rate of fire values.

Lever Action Rifle changes: In addition to adding caliber swaps and ammo types, the lever action rifle also now receives +3 ammo capacity when using the Long Barrel or Long Ported Barrel options (they have longer tubes... why not use them?)

All vanilla and Far Harbor firearms are supported as of version 1! Note that not all categories are available for every gun (for example, there is no automatic fire mode for the flare gun or double barrel shotgun since it doesn't make sense).

New caliber/fire mode combinations will spawn from enemies and be sold by vendors!
If you encounter any issues or crashes, DO NOT post to the comments. Your issue will probably get lost.
Help me help you. Submit a Bug report with your exact weapon build (eg. receiver, barrels, muzzles, etc.) and if you use any other mods that might conflict.


10mm Pistol - Caliber Swaps | Ammo Types | Fire Modes |Naming convention changes for new calibers 
.44 Pistol - Caliber Swaps | Ammo Types |Naming convention changes for new calibers 
Assault Rifle - Caliber Swaps | Ammo Types | Fire Modes |Naming convention changes for calibers
Combat Rifle - Caliber Swaps | Ammo Types | Fire Modes |Naming convention changes for new calibers 
Combat Shotgun - Ammo Types | Fire Modes
Deliverer - Caliber Swaps | Ammo Types |Naming convention changes for new calibers
Double Barrel Shotgun -  Ammo Types
Hunting Rifle - Caliber Swaps | Ammo Types |Naming convention changes for new calibers
Minigun - Caliber Swaps | Ammo Types |Naming convention changes for new calibers
Pipe Gun - Caliber Swaps | Ammo Types | Fire Modes |Naming convention changes for new calibers
Pipe Bolt-Action Gun - Caliber Swaps | Ammo Types |Naming convention changes for new calibers
Pipe Revolver - Caliber Swaps | Ammo Types |Naming convention changes for new calibers
Flare Gun - Caliber Swaps | Ammo Types
Lever Action Rifle (Far Harbor) - Caliber Swaps | Ammo Types |Naming convention changes for new calibers
Radium Rifle (Far Harbor) - Caliber Swaps | Ammo Types | Firing Modes |Naming convention changes for new calibers

Only the weapon listings (e.g. 10mm Pistol, .44 Pistol, etc.) and receiver object modifications (e.g. Hunting Rifle .50 Receiver, Assault Rifle Automatic Receiver, etc.) are tweaked by this mod. No changes have been made to loot lists or NPCs.


Pick which version is relevant to you (DLC Edition or No DLC) and drop the ESP file into your Fallout 4 Data folder.

To uninstall, just delete the ESP. Easy!


I'm trying to decide if / how to support energy weapons and non-conventional firearms (broadsider, harpoon gun, syringer, etc.) More to come on this...


Any mod that tweaks the vanilla weapon receivers or weapon properties will create a conflict. To solve for this, simply create a merged patch. If you do not know how to do this, try Google or YouTube for a quick and easy tutorial. I did a quick search and found this video here 
in less than 20 seconds.

If you make a compatibility patch, you are free to release it to the public if you so desire.

I do not create patches for other mods. It's simply too time-consuming because there are so many mods out there to account for. Sorry!




Any permitted use requires citation of myself as the original authors. You may not use the contents of this file or commercial uses.

No need to ask if you would like to release updated versions of the ESP here. Please just link back to this original file and cite the authors for their contributions. Thanks!


Myself (Undyne777) for creating the original mod within FO4Edit and the Creation Kit
cooleo for his help with the v1.2 fix for suppressor projectiles and beyond!
Hlp, Zilav and Sharlikran for their test distribution of FO4Edit on Nexus
Bethesda for the Creation Kit and the base FO4 set-up for me to work off of.


Creation Kit