If properly stored it could possibly be shootable although most likely corrosive. Alot of older European powders were/are double based, meaning it contains nitro-glycrine as well as nitro-cellulose. According to Frank Barnes "Cartridges of the World" this makes them somewhat more susceptible to decaying and becomng less stable. This in turn can yield pressure spikes above and beyond it's original design parameters. Pull a bullet from a case and smell it carefully. If it is sour or acrid smelling I would stay away from it. If it is, I would salvage the bullets and toss the rest, as some of the primer components MIGHT create issues with the structural integrity of the brass cases. (Fulminate of mercury in primers= brass and mercury don't play well together iirc)
Hundreds of millions of .303 British was loaded with Cordite brand powder (stick shaped). A web search will tell you if there any issues to give you pause about using it.
My comments are based on reading the aforementioned book probably 30 years ago so I might have
mis-remembered
some of the specifics. The web is a wonderful thing.
ETA: Well after looking at the pictures...... I have never seen pictures of cordite in anything but long strands. So the .303 might be ammo made in the colonies (India??) with short cut powder??? More research is required. Not surprised the Lebel ammo has cordite looking powder as well as the Brits and French WERE allies, so likely they shared some material over the years. The Krag loaded with spherical and or flake is easily possible as both those powders were in use at that time as well.