We don’t have much information about this rifle, but we do know that is was a prototype direct gas impingement rifle in 6mm, built at the Puteaux Arsenal. It had an overall length of 50″, weighed 9.4 pounds, and used a 6-round integral magazine. Jean Huon, in his excellent book Proud Promise, suggests that this may have been an early forerunner of the M1917 automatic rifle the French would later adopt. It has a gas tube under the barrel, which operates a rotating bolt.
An outstanding reference on the development of French military rifles is Jean Huon’s Proud Promise: French Autoloading Rifles 1898-1979.