Incredibly simple and easy to mass produce, the Sten Gun Mk.2 cost only about $6 to manufacture. Fortunately, however, the 9 mm round and relatively slow rate of fire - approximately 550 rounds per minute - provided an exceptional amount of stability. The only serious drawback of the Sten gun was that the effective range was only slightly less than 100 metres. Nonetheless, so popular was the Sten Mk.2 design that more than 4 millions were produced.
Sten Gun Mk.2 on Wikipedia