The SCK-65 and the later SCK-66, also known as the New Nambu M65 and M66 respectively, are prototype Japanese submachine guns.
Development was entrusted to Shin Chūō Kōgyō K.K. (now known as Minebea Co.) who was known for the production of the Sumitomo NTK-62 and Howa Type 64s, and were regarded as having the experience of building such weapons.
The weapon never advanced beyond prototype stages; no samples appear to exist today.
The SCK-65 is a blowback weapon that fires from an open bolt; the weapon is also select fire. The ejection port is situated on the left side of the firearm and is usually covered by a dust cover; this cover has to be opened before the gun can be fired as it contains a projection that locks the bolt closed when the cover is closed.
The weapon also has a rather oddly-placed grip safety in the form of a lever located behind the actual magazine well; this means that the weapon can only be fired if the magazine well is held, with the shooter's off hand applying pressure on said grip safety. The weapon has a rather tiny non-reciprocating charging handle located on the right side of the weapon. The barrel is enclosed into the tubular jacket which appears to have no cooling measures.
- SCK-66/New Nambu M66
Slightly smaller and lighter variant of the SCK-65. Has a slightly lower rate of fire.
- The SCK-65 (and the related SCK-66) are the only Japanese firearms that are known as submachine guns by the Japanese National Police Reserve.