Check out Magpul STR Low-poly 3D model on CGTrader for $15. High-quality mesh by olalopa: 11000 polys, 5480 vertices. PBR, Textured, UV Mapped.
OBJ (OBJ, filesize: 1.12 MB), FBX (Autodesk FBX, filesize: 434 KB), ZTL (Zbrush, filesize: 449 MB), ABC (Alembic, filesize: 824 KB), DAE (Collada, filesize: 1.69 MB)