The K-13A1 is a standard M16A1 with several modifications such as rails and a M202 grenade launcher. The M202 was an experimental grenade launcher that had good field results from which the M203 was derived. This rifle was made to be a cheap effective assault rifle for countries that cannot afford modern assault rifles.
The K-16A1c is the carbine variant of the K-13A1 comparable to the M-4 carbine.
The K-13A1s is a .45 ACP submachine gun variant of the K-13A1 for use as a personal defence weapon, officers weapon and vehicle crew weapon.