The Sjorgen rifle and shotgun designs definitely fit the description of Forgotten Weapons. Developed in Sweden, the Sjogren system used a fixed barrel and recoil-operated action in both a 12 gauge shotgun and .30 caliber military-style rifle. It was claimed to have very light recoil, as a result of the energy absorbed by the action cycling, though I doubt this recoil reduction was any more significant than today’s autoloading firearms.
The Sjogren rifle was submitted to British military trials, but failed to garner enough interest to see further testing or use. The shotguns saw some commercial sales, and can still be found today from time to time, but were not successful enough to stay in production very long. Not much information is available on the guns, but we do have a copy of an article describing them in some technical detail from a 1908 edition of Engineering magazine: