France began working on developing military self-loading rifles virtually as soon as the 1886 Lebel was adopted, and they would pursue a pretty elaborate series of trials right up to World War I. One series was developed by Etienne Meunier at the Artillery Technical Section using gas operated mechanisms, and designated the A series. The B series was the work of M. Rossignol at the Musketry School, using mostly direct gas impingement systems. The C series was designed by Louis Chauchat and M. Sutter at the Puteaux Arsenal, and these were long-recoil actions. Trials commenced in 1911 and 1912 on the latest rifles from each series, and ultimately none was judged really ready for military service - although the A6 Meunier would be produced in small numbers (about a thousand) and issued in 1916.
This particular rifle is a C6, from Chauchat and Sutter. The C7 was in the formal testing, and this C6 is a very similar rifle. It uses a long recoil action, a unique locking system with two pivoting locking lugs somewhat similar to the Kjellman system, and a remarkably powerful 7mm rimless cartridge fed from 6-round Mannlicher type clips. It was deemed too complicated at trial, not surprisingly.
M1915 Chauchat Automatic Rifle: https://www.full30.com/video/5933a44c278a66269fcdf19cde11261c
M14 Gras Conversion to 8mm Lebel: https://www.full30.com/video/93193357dc87dba73b9583a9d6c22d77
French Rolling Block in 8mm Lebel: https://www.full30.com/video/05480fd232e181053879a96dbb33393d
RSC 1917 Semiauto Rifle: https://www.full30.com/video/b3da75e7a61c5236e490ce0cbd738e3b