Korean firm Dong In Optical specializes in red dot sights for machine guns, miniguns, grenade launchers and auto-cannons.
The Model DCL100 Red Dot Sight (below) is designed specifically for the FN Minimi / M249 and FN MAG / M240 light machine guns. It is seen here mounted on the Minimi Para, FN’s short 13.7″ barreled, collapsible stocked, machine gun.
I have an overwhelming desire to mount one of these on a Ruger 10/22
A big thanks to Groot Mamba for the photos.