Daewoo Precision Industries K1

The Daewoo Precision Industries K1/K1A is a South Korean selective-fire assault rifle developed by Agency for Defense Development (ADD) and manufactured by Daewoo Precision Industries (now S&T Motiv) and Dasan Machineries (since 2016). It entered service in the Republic of Korea Armed Forces in 1981. Although the K1 uses .223 Remington, it is classified as a submachine gun by the South Korean military and the manufacturer, because the K1 was intended to replace the M3 submachine gun.
Development.
In 1976, the ROKA Special Warfare Command requested a new weapon to replace the old M3 submachine gun. In the following year, ADD launched a project derived from the XB rifle, which started in 1972 to replace licensed M16A1s with indigenous weapons. Under the demands of the ROKASWC, the new submachine gun must acquire greater firepower, light weight, cost effectiveness, and easy access to spare parts. The first prototypes were made in 1980, and entered service in 1981 after series of field test. 
But due to the design of its flash suppressor, the K1 exhibited serious problems in service with the ROK armed forces. The original version had excessive recoil, noise, flash, and weak stock due to increase in firepower. These problems caused difficulty in aiming especially during night operation.
These shortcomings were later fixed by the development and adoption of a new flash suppressor, which has three holes in the top right quadrant to limit muzzle flip under rapid fire and reduces flash to one-third of that of the early K1. This new version of K1 is known as the K1A and its production began in 1982. All K1 submachine guns in service were subsequently modified to the K1A standard.
The K1A is often mated with the PVS-4K rail integration System. It is seen as a potential candidate for the "Warrior Platform", a Korean next-generation infantry project.
Since 2014, newly produced and repaired K1A received new barrel suited for firing 5.56x45mm NATO ammunition.
Differences.
Most of the time, K1 submachine gun is regarded as a shortened or carbine version of Daewoo Precision Industries K2 assault rifle. However, although the two guns share development history they are very different from each other for the following reasons:
The carbine version of K2 named K2C was developed and shown to the public in 2012 by S&T Motiv.
Future replacement.
The S&T Motiv K2C, an upgraded carbine version of the K2 rifle, was provided to the Republic of Korea Army Special Warfare Command for trial. After a series of tests, K2C was rejected. Instead, the Republic of Korea Armed Forces launched a competition for replacing K1A with new rifle.
On 13 June 2020, the Republic of Korea Army Special Warfare Command announced that the DSAR15PC had been selected as its new service carbine to replace the K1A carbine. The DSAR15P is based on the CAR 816 and other AR-15 platforms, with the carbine version having an barrel and weighing . 1,000 carbines will initially be delivered to gather user feedback, with 15,000 to be delivered by 2023.