If we presume a pre 1915 origin of a French semi-automatic rifle design one runs into the then prevailing expectation that an infantry rifle has to reach out to long distances. This demands a heavy charge and heavy bullet. The lightest OTL being the Italian 6.5x52. Thus was pretty well taken as a given requirement across the world, in the absence of large numbers of machine guns and an appreciation of this being the role of the heavy machine gun not yet being common.
The result is that a French WW1 semi-automatic rifle will have to use a full power cartridge which adds to the stresses of period metallurgy and design. This is then compounded by the 8mm Lebel being a horrible design for anything other than manual loading. A cobbled together in a hurry grossly tapered and necked down rimmed .45 Gras black powder cartridge designed to go into a modified paper cartridge Chassepot of the 1860's.
If one can get the French army to increase it's numbers of 8mm machine guns and release the rifle from the long distance task then one could have them decide that this is the time (pre war) to get a modern rimless round and download it to practical conscript rifle ranges. Not quite an 'intermediate' round as IOTL perhaps but maybe a lesser Italian size. Perhaps a 6x50. The chosen method of action is immaterial but this would be within the metallurgy of the day even if the end result would be heavier than we would make today. Also the tactical concept change would go with a shortening of the barrel to a carbine length.
However, given the actual thinking of the day, I cannot see them going for anything less than a Lebel equivalent but in semi-automatic form. The sheer numbers of rifles needed militate against a change from 8mm Lebel when you consider what they dredged up to make up the numbers IOTL. It would need a POD well before WW1 to see the numbers and manufacturing capacity and ammunition stocks allowing anything other than 8mm Lebel to be the standard.
The result is that a French WW1 semi-automatic rifle will have to use a full power cartridge which adds to the stresses of period metallurgy and design. This is then compounded by the 8mm Lebel being a horrible design for anything other than manual loading. A cobbled together in a hurry grossly tapered and necked down rimmed .45 Gras black powder cartridge designed to go into a modified paper cartridge Chassepot of the 1860's.
If one can get the French army to increase it's numbers of 8mm machine guns and release the rifle from the long distance task then one could have them decide that this is the time (pre war) to get a modern rimless round and download it to practical conscript rifle ranges. Not quite an 'intermediate' round as IOTL perhaps but maybe a lesser Italian size. Perhaps a 6x50. The chosen method of action is immaterial but this would be within the metallurgy of the day even if the end result would be heavier than we would make today. Also the tactical concept change would go with a shortening of the barrel to a carbine length.
However, given the actual thinking of the day, I cannot see them going for anything less than a Lebel equivalent but in semi-automatic form. The sheer numbers of rifles needed militate against a change from 8mm Lebel when you consider what they dredged up to make up the numbers IOTL. It would need a POD well before WW1 to see the numbers and manufacturing capacity and ammunition stocks allowing anything other than 8mm Lebel to be the standard.