If your looking at getting started in the world of 3D printed weapons, the 3D Printer Buying Guide is a good place to begin!
The LR-308 Super Lower is a 3D printable lower receiver compatible with DPMS or LR-308 uppers. It’s designed for upper receivers chambered in 7.62 x 51, 6.5 Creedmoor, and other high powered cartridges. It uses a steel buffer band and support rib to provide the needed level of durability.
The lower is compatibility with ambidextrous selector switches. This design includes custom support.