Gene,
Bet your French gun has tight bores. They work best in guns that are snug. My lefty Darne had a fearsome backbore perpetrated on it, some time before my ownership. They didn’t work in that one.

I would think you might get away with hunting Snipe, woodcock, grouse, or quail with the 7 1/2 loading. Pheasants, not so much.

Best,
Ted