FYI, it's not a Flare, it's payload is Magnesium and makes it an "Incendiary" round. Made from mixed small and larger pieces. The lg. pieces will do the major fire damage and the sm. pieces help light them up in the barrel which is why NO Semi-Auto guns (gas port for the action) should ever use them.
Magnesium doesn't go out easily and will burn under water
. Fire depts. dread Magnesium fires because they can't use Water. But, it's much safer than any Phosphorous Shell or Flare to store.
From Wiki; Magnesium is capable of reducing water to highly flammable hydrogen gas and as a result, water cannot be used to extinguish magnesium fires; the hydrogen gas produced will only intensify the fire.
Magnesium also reacts with carbon dioxide to form magnesium oxide and carbon:
hence, carbon dioxide fire extinguishers cannot be used for extinguishing magnesium fires either.
Sand or a Dry Chem. extinguisher are the only things that will put it out (if it's much larger pieces of Mag.)
If you were to shoot them at a Boat attacking you and even a few of the pieces burn through into the Bilge, that Boat is basically gone!!