Here is a quick video on shooting Supine and when you may need to use it.
AR NERDS REJOICE, Classic Ruger and a BIG Glock Fail - TGC News!
Final Prices: Rock Island December 2017 Premier (#72)
Slow Motion: StG-45(M) Reproduction
Manca's shooting instructions
BCM Training Tip - Vert Grip Placement.mp4