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The origins of flap-locking (as used in the G41(W), G43, DShK, DP, and RPD, among others) goes back to a Swedish Lieutenant Friberg in 1870, who patented the system. At that time, however, the fouling endemic to black powder made self-loading firearms effectively impossible and so the concept would have to wait until the invention of smokeless powder to become practical. The first to actually build a rifle or machine gun (he did both) was a man named Kjellman working at the Stockholms Vapenfabrik factory in Sweden, at the turn of the 20th century. The factory was the former Nordenfelt facility, and was trying to expand into small arms manufacture by making this Friberg/Kjellman rifle for international military contracts.
About 50 examples were made in a variety of calibers and configurations, but no contracts were obtained and the rifle never entered mass production. Mechanically, it locks using the flapper system and cycles with a short recoil action. What is particularly unusual about the design is the use of a lever arm to both open and close the bolt without the aid of a recoil spring. This actually works, but feels very counterintuitive to handle by today’s standards!
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