These are dummy cartridges, used for practise loading the guns etc., preventing the use of a life cartridge. the are filled with hardwood, oak, to simulate the weight of the gunpowder, and a big brass cap, haube is soldered on it. the two i have a re recovered form the sea, and loaded with sold, ofter being 5 years or even more now, out of the sea, thill the salt is getting out of it,about a few teaspones a year.
the picture shows one of the cartridges and the salt getting out of it. (the big bubba on the right)