Prototype Friberg/Kjellman Flapper-Locking Semiauto Rifle

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!


  1. No… Roots Degtyarev lock Bolt system – “double” Odkolek (Benet-mercie), Mauser and Restl locking system. For example – patents US nombers 486938, 918760, 943949, 1095739.

  2. This gun is uniquely simple! And you won’t have the bolt slam your thumb during the loading cycle, which is great for user friendliness. There seems to be a need for a receiver cover (mud isn’t nice to open-action weapons), but sadly this rifle didn’t get developed any further.

  3. Yes, it is unusual system and rather meticulous one.
    One thing which observer may not realize, with two flapper locks, it is only one which is fully loaded (well there is some elasticity…), the other kind of assists. Other way to assure it is balanced on both sides is to make receiver and lock arms really large and heavy. Ideally, you may want to group all involved parts, which defeats interchangeability. Not really good system overall.

  4. That was interesting and very much a Forgotten Weapon. I have not been able to pull up FW video’s on Full30 for several days now but that might just be my satellite hook up I have to use from the Virginia wilderness.

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