When I was a few years younger and lived in the Lake District (Cumbria) I was not far from a stretch of moorland that the Army used in WW2 for practice, armed with a metal detector and a shovel I spent many a summer day searching the moors for spent cases or something interesting, found everything from mortar fins to cap badges etc plus millions of .303 cases and quite a lot of live rounds.....
The live rounds were not always good condition so would break them open and extract the cordite....... the cases were dated 1941, 1942.