The aim was to have a brand new heavy machine gun design, that fires the same type of .50 cal rounds as the M2HB machine guns and to have the gun parts more readily available in view of easing SAF's chain of logistics and supplies.[1]
Design
The CIS engineers learned from the lesson of the canceled (lack of funding) American "Dover Devil GPHMG" program known as the Special Projects Group at Picatinny Arsenal led by Charles J. Rhoades. Curt Johnson and Phil Baker developed the original concept to create a modular weapon suited for modern tactical doctrines and production techniques.[3] In 1988, CIS introduced the new 12.7mm machine gun which was aptly named as the CIS 50MG, after two years of development and testing phase.[2]
As the STK 50 MG is a gas-operated, air-cooled, belt-fed weapon, the gun is operated using dual gas pistons, located in two gas tubes placed on either side of the barrel. The barrel is locked by means of a rotary bolt with multiple radial lugs that engages the barrel extension, eliminating the need for headspace adjustments. The CIS 50MG utilises the same "constant recoil" system used in the Ultimax 100 and it also has a quick-detachable barrel equipped with a carrying handle to facilitate the ease of barrel changing under combat situations or during operational manoeuvres.[2]
Indonesia: Licensed production by PT Pindad as the Pindad SMB-QCB (Senapan Mesin Berat-Quick Change Barrel) for the Indonesian military.[1][7] In 2018, it has been renamed as SM5.[8]
^Using the Wayback machine on this CIS 50 page indicates that the CIS 50 MG name was used until 2016, when it changed to the STK 50 MG name as seen here.