Fallout 4

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About this mod

This mod adds a SIG Sauer MPX Gen. 2 SMG to the Commonwealth. ESP and ESL versions available.

Permissions and credits
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Updated FAQ as of September 2023. See below.

Xbox port available, courtesy of user GoodnightEngland et al.

This mod adds a SIG Sauer MPX Gen. 2 SMG to the Commonwealth. It starts appearing on higher ranked gunners and miscellaneous boss types from level 20. Vendors who specialize in guns will start taking in these from level 12. The mod comes in both ESP and ESL formats, and is currently available in 2K (default) and 1K textures versions.

Please note that the ESL version of this mod is experimental. This means that future updates on the ESL version may or may not break any MPX you have in your save.



By popular demand I've included a list of features this mod includes.

  • 10 receiver upgrades
  • 3 form factors (compact, standard, carbine)
  • 8 custom barrels at various lengths per form factor
  • 3 caliber choices (.38, 10mm or .45)
  • 3 foregrip options (standard, vertical, magazine well grip)
  • 4 pistol grips
  • 4 magazines plus Quick Eject versions
  • 7 assorted muzzles
  • 6 receiver and handguard paintjobs
  • Select fire mods with customizable fire rates from 657 to 900 RPM
  • 6 sights including various current SIG Sauer optics line-up
  • Toggle for overlay, night vision and see-through for scopes
  • Options for sights mount position and different see-through reticles
  • 2 automatic non-silenced sound mods
  • 3 stocks

Custom animations
  • All custom animations for first person, third person, power armor, NPCs, synths (about 250 animation files)
  • Animations for all foregrips and magazines
  • Optional custom sprinting animations by WarDaddy

Custom sounds
  • All custom sounds for player, NPCs, different fire rates, silenced, automatic and single fire

Leveled list integration
  • Modest injection using WeaponLLInject courtesy of a_blind_man.

Stuff used

  • Modeled in Blender 2.79
  • Textured in Substance Painter
  • Animated and custom collision meshes in 3ds Max 13/15
  • Sound design in Steinberg Cubase
  • DirectXTex / Compressonator for DDS compression
  • Vscode for Papyrus/maxscript
  • Blender/Krita/Gimp for reticles, logos and graphics
  • Nifskope, Material Editor, hkxpack, havok2fbx, CK, FO4Edit, FOMOD Creation Tool

Thanks to the people involved in making the tools that enable us to do this. This project was done in love of modding, and this mod a humble gift back to the Nexus after a decade of lurking.

On reporting bugs

Consider this mod in perpetual beta. If you encounter any bugs, I'd appreciate if you let me know using the bug tracker or comments section. A lot of work has gone into testing, but I'm only one person - some things may have slipped past me. 

That said, if you do plan on reporting an issue, please be verbose and provide as much information as possible. Try to give adequate steps to reproduce the bug, screenshots or video if applicable. If there's anything I can fix, I will put an effort into correcting it. However, I will cordially shut down bug reports that provide no information for me to debug. Thanks!

Can I use this mod or any of its assets in my own mod/collection?
  • Is your mod/collection free for anyone to download and use? Then yes.
  • Is your mod/collection behind any sort of paywall eg. Patreon or other paid services? Then no.

[Insert question about console version]

  • I don't own a console and don't have resources to maintain this mod across multiple platforms. However, user GoodnightEngland has stepped in and helped provide a port to Xbox. You can find it here.

How to install
  • Either by using latest version of NMM or by manually copying files. All files are archived for easy manual installation. Remember to activate the plugin using either NMM, the in-game "Mods" menu or by adding the plugin to your plugins.txt.

There are multiple versions. Which do I download?
  • I'm offering both 2K and 1K versions at the moment. The 1K version means that the maximum size texture is 1K, making the mod take roughly 1/3 the size of the default 2K version. Download the 1K version only if you suffer from performance or are on a strict disk space quota.

Do I need the "Update" file?
  • The update file includes only the files touched since the previous version. It is offered for those who don't want to re-download the whole package. The update file requires that you have a full file of a previous version.

How can I shamelessly spawn the weapon?
  • If you've never done this before, see this. Otherwise "help mpx 4 weap" and "player.additem xx000F99" where xx is the first hexadecimal denoted in the console entry.

I installed but the vendor isn't showing the gun
  • Wait until the vendor restocks their inventory - usually when they open shop the next day.

Notes about ESL
  • Since the mod makes no external dependencies, it qualifies to be in the new ESL format. However, this makes updates to the mod much, much more difficult because of size and FormID address restrictions. Please understand that by using the ESL version of this mod, you are accepting the risk that any future ESL updates may or may invalidate any MPX you have in your current save.

Scripts involved?
  • Just some injectors. Nothing that runs in the background. 

Uninstall / Mid-Playthrough Hazard
  • There should be no issues installing this mid-playthrough. During uninstall, script-added forms may stay behind until the game automatically does garbage collection. There are no scripts running, checking or listening in the background at any time. Still, you should adhere to basic common sense of handling mods.

Requirements? DLC? AWKCR? See-Through? F4SE?
  • Just the base game. The mod is completely self-contained.

It doesn't look exactly like the real the MPX
  • Creative liberty.

  • Pretty normal. Poly density increased later in development, which may explain the jump in the fidelity across different attachments. Diffuse and spec/normal textures use DXT1/BC5 subformats for maximum compatibility. Texture dimensions range from 512 to 2K.

  • Where applicable.

[Insert question about damage multipliers]
  • It should be balanced according to its vanilla counterparts, with added upgrades which makes it a viable toy even for end-game. There are multiple calibers to choose from and I'll monitor feedback to make it fair and balanced. However, this mod will never have straight-out damage multipliers, please see some other weapon mod for that or learn to use FO4Edit.

[Insert question about leveled lists]
  • The MPX is injected into the leveled list of gunners flagged with automatic weapons, and starts to appear on them from level 20. Otherwise, some vendors who specialize in guns start taking these in around level 12. It's not meant to be a common find. However, please let me know if the drop rate is too low or too high.

[Insert question about Visible Weapons]
  • I won't be adding any. You are free to create a patch for it. Let me know and I'll add a link to the patch.

Can you please make a [insert attachment/weapon] ?
  • In general, no. Sorry! I know it's boring to hear this, but consider the amount of time it takes to create just one single asset (days). It's impossible to satisfy everyone, and I need to treat everyone equally.

Known Issues

Disappearing sub-mod slots
  • When you have multiple MPXs of different configurations in your inventory, mod slots such as barrels, muzzles, etc. may disappear from the workbench menu list. This happens because Fallout 4 doesn't fully support custom sub-categories. The game will lock mod slots to whatever weapon you have equipped. To bypass this issue: Exit the workbench, go to your pipboy and equip the weapon you plan on modding, enter the workbench again and the slots will show.

3rd person gun bash left hand loses IK at end of animation
  • Limitation of vanilla behavior logic where the end clip of RifleMeleeForwardPowerAttack erroneously cycles left hand IK through the default rifle pose before arriving at the assembly transformation. Can be fixed by using a custom WeaponBehavior.hkx with a boolean flip. However, this could potentially cause conflicts, so until I learn how to make a custom wrapper behavior this stays unsolved.