Yesterday I found this model from a year and a few months ago and I decided to finish it. The geometry is horrible and the textures are all 2K because Substance Painter just shuts down when I try to export at 4K resolution, but I'm pretty happy with the result.
Game-ready MK18 with Trijicon MRO sight. All parts are movable and removable. 2K PBR textures, 2 materials. The tricount for this one is like 40K triangles, didn't know much about optimization back then. I'd love to see it animated or something so if you're interested just hit me up. You can download for free on Sketchfab. Cheers.