How to install:

Check for possible conflicts before installing all these mods, go to your lml folder and search for:

weapons.ymt
catalog_sp.ymt
shop_items.ymt

Delete any mod that have these files.
These three files are the most important ones.

1. Download all the mods below:

1899 Firearms
https://www.nexusmods.com/reddeadredemption2/mods/1273

Firearm Cosmetics
https://www.nexusmods.com/reddeadredemption2/mods/1781

GunFX
https://www.nexusmods.com/reddeadredemption2/mods/1186

WhyEm's DLC - DO NOT INSTALL
https://www.nexusmods.com/reddeadredemption2/mods/671

Eastern's Epic Extras - DO NOT INSTALL
https://www.nexusmods.com/reddeadredemption2/mods/1505

Gonpachiro's Fancy Atelier - OPTIONAL
https://www.nexusmods.com/reddeadredemption2/mods/1795

2. Install 1899 Firearms, refer to its installation instructions.

3. Drag and drop the two folders in this zip file(WickedHorseMan and andr3) to your lml folder.

4. Open WhyEm's DLC .zip and drag and drop its Item_Textures folder to the "The Trifecta Redux", folder path "lml/andr3/The Trifecta Redux/Item_Textures".

5. Open EEE's .zip and drag and drop its Item_Textures folder to the "The Trifecta Redux" folder. Overwrite when asked, folder path "lml/andr3/The Trifecta Redux/Item_Textures".

6. OPTIONAL: Open GFA's .zip and drag and drop all its texture files to any of the numbered folders inside Item_Textures of the "The Trifecta Redux" folder, folder path "lml/andr3/The Trifecta Redux/Item_Textures".

7. BEFORE STARTING YOUR GAME, go to "Settings", then "Graphics" and change to "Vulkan".

8. Job done!