the Lebel cartridge went through changes over its lifetime. look on the barrel chamber area for a mark "BALLE" followed by a letter to idicated change to.
and i would be leery using modern ammo, only because original French rounds had a groove circling the primer to catch the spitzer bullet as they are loaded. this groove was to prevent pointed bullets from setting off the cartridge ahead of it in the magazine. here is some reading for you. 8mm Lebel - The Gun Wiki