Article about: Just two finds on a recent Normandy trip - close to St Lo, what I assume to be a mortar fuse and an M1 case. The live round was found along with a number of cases closeby some months earlier
It is the lot of a relichunter to have days like this......trust me I have had them to.
If you are searching near St Lo then I am afraid you are highly likely to be doing so illegally (unless you have written permission of the 'state' legislator) and the French authorities have the power to impound you, your gear, your car and slap you in jail for a couple of weeks, even before any hearing.
Take my advice...stick to areas less risky ! You can find tons of stuff in the UK and on beaches and not break any laws.