SDAR 5.56 mm

 is a weapon in Project Argo.

Summary
Special Dual-medium Assault Rifle is a bullpup rifle specially designed to allow shooting both on alnd and under water. It uses standard 5.56x45 mm rounds or special supercavitating ammunition which is efficient when used under water. But still, when under water, its range drops rapidly from 35 meters in 10 m depth to 13 meters in 40 m depth.