The Madsen M-50 or M/50 is a submachine gun introduced in 1950, an improved version of the M-46. It was produced by the Danish company Dansk Industri Syndikat of Copenhagen, Denmark. The company was otherwise known as Madsen after its founder Vilhelm Herman Oluf Madsen.
The weapon was unusual because the frame was of the clamshell design. The weapon opened from the front and swung open, like a clam's shell, and the interior parts could be cleaned and replaced. The nut that secured the barrel to the frame secured the frame shut. The few removable interior parts consist of the bolt (with fixed firing pin) and operating rod/recoil spring.
The butt of the side-folding stock was wrapped with leather to provide a non-slip surface. The magazine well had a grip safety that would not allow the weapon to fire unless it was securely gripped by the bracing hand. There was also a simple trigger block safety on the left side just above the trigger group. The simple post-and-notch sights were both on the left side of the frame to allow them to line up properly. The weapon's single-stack double-column 32-round magazine was of poor design and was prone to jamming even if kept clean.
The CIA and US Special Forces procured the M-50 in the Southeast Asian Theater as a sterile weapon. It was manufactured by a neutral country that couldn't be traced back to their forces. Many had already been sold in Southeast Asia so it was already a common weapon in the area in the 1950s and 1960s. In fact, some had been acquired by the Viet Cong from their opponents.