During and after the Korean War, the South Korean military was armed with American weapons – M1 Garands, M1 Carbines, M3/M3A1 Grease Guns, and so on. In the 1970s they wanted to modernize their equipment, and looked to the US. South Korea purchased M16A1 rifles form Colt, and the Daewoo conglomerate obtained a license to manufacture them. Around the same time, they began a development program to produce a new array of Korean domestic small arms. The first result was the K1, a 5.56mm carbine (designated a submachine gun) to replace the Grease Gun.
The K1 used the AR15 gas system and AR15 fire control system, but couples with a right-side charging handle and a bolt carrier and recoil spring setup similar to the AR18, negating the need for a recoil spring in the stock and allowing the use of a wire collapsing stock. In its military form, it had a 10.4 inch barrel, and had both semiauto and full auto fire settings. The K1 remains in South Korean service today in the K1C form, updated to allow mounting of optics and other accessories.
In the 1980s and early 90s, the K1 was imported into the United States under several different names, including the K1A1, MAX-1, and (in the case of the rifle in today’s video) AR-110C. All had barrels lengthened to 16 inches to avoid the NFA, and were semiautomatic only.