I made this model 100% in Blender to showcase it's Texture Painting features.
This model is inspired by a model here on Sketchfab. I made this model while teaching Blender's Texture painting features to a group of students.
Here is the model I was inspired by: https://sketchfab.com/3d-models/srr-custom-acb02d27977e4daf98aeb21c35c93714
It is made by McCarthy3D: https://sketchfab.com/joshuawatt811
You can buy the original gun model for just $10 on his page.