I came across this image in ‘The Book of Colt Paper 1834 – 2011’ by John Ogle.

This is not the Knights Armament M4/M5 RIS/RAS systems. This is completely different.

I have been fortunate enough to discover that one of the engineers that helped design the system is in my Facebook group. This has turned into a little bit of a ‘rabbit hole’ research project for me. I will put together a write-up and post it here soon.