Low-poly 3D models of Stylized double-barreled Shotgun (2142 polys) and Shotgun Shell (30 polys) don't contain any n-gons and have optimal topology. The archive with textures contains such two folders:

Double-barreled Shotgun Textures (2K) - base color map, metalness map, normal map (OpenGL), roughness map.

Shotgun Ammo Textures (512x512px) - base color map, metalness map, normal map (OpenGL), and roughness map.

Additional information.

Files and Formats: OBJ, FBX, ZTL, MA, MB, Folders with textures

Geometry - Polygon mesh

Unwrapped UVs - Non-overlapping

Images were rendered in Marmoset.