Paul Ribeyrolles was the manager of the Gladiator bicycle factory, and by 1918 he had significant experience in small arms design, having been a core member of the team that designed and built the 1915 CSRG Chauchat automatic rifle and the RSC-1917 semiautomatic rifle. These were forward-looking weapons, the first of their types ever to be successfully used in combat. Ribeyrolles continued to pursue the next generation of infantry small arms, and in the summer of 1918 he presented his 1918 automatic rifle for military testing at Versailles.
The model 1918 met most of the requirements to be considered an assault rifle by today’s standards – it used an intermediate cartridge, it could fire in both semiautomatic and fully automatic modes, and it was fed by detachable box magazines (with a capacity of 25 rounds). The cartridge it used was a modification of the .351 Winchester WSL cartridge, modified to be semi-rimmed and to use an 8mm Lebel armor-piercing bullet. Unlike modern weapons of this type, however, Ribeyrolles’ rifle used a simple blowback action and this required a quite heavy bolt to work properly. Unloaded, the weapon weighed 11.25 pounds (5.1kg), and the long receiver necessary for the bolt to effectively decelerate gave it an overall length of 1.09m (43 inches) – this was long and heavy for its capabilities. Still, it was conceptually pretty advanced for 1918.
The biggest problem which prevented the gun from seeing any military interest was reliability. At the 1918 trials, it was very unreliable – the one source I sound said that 53 malfunctions were had in 75 rounds of semiautomatic fire. That is definitely a sign of a design not ready for adoption!
Ribeyrolle brough the gun back for more testing in the summer of 1921 at Camp de Chalons, but it does not appear that he had fully cured the reliability problems. In addition, the gun’s futuristic concept left it out of place in the arms lineup envisioned by the French military. It was too heavy and bulky to fill the role of a personal weapon like a submachine gun (note that the SMG ultimately adopted by the French, the MAS-38, is one of the smallest and lightest such guns ever used by a military power). And because of its intermediate cartridge, with a 400 meter effective range, it was considered too underpowered to fill the role of an infantry rifle. And thus, it was rejected, never to be seen again.
I do not know how many examples of the Ribeyrolles 1918 were actually manufactured, but it was certainly only a few – apparently only 3000 rounds of its ammunition were made for the 1921 testing. To the best of my knowledge, no examples survive today – any that were preserved after the trials were lost or destroyed in the chaos of WWII occupation and liberation.