When Colt started manufacturing the M-16/AR-15 in the mid 1960s they created a LMG to go along with it.
The often forgotten CMG-2 “Colt Machine Gun” narrowly lost a bid to the Stoner 63 for service with the Navy SEALS despite being a light weight and reliable firearm. Colt tried to resurrect their CMG in the 1970s by upping the caliber to 7.62mm and renaming it the CMG-3.
Only 5 units were ever made. Following a battery of military tests, the CMG-3 was found wanting with a service life of a mere 35,000 rounds. The weak receiver was prone to fractures and the contract lapsed before Colt could make any improvements.
Of those original 5 only 2 remain. The one featured in this video is serial number 1, and is still in decent enough condition for a brief day on the range.