I once spent an enjoyable afternoon with a verey pistol and a box of flares at one of the remoter northern outposts of Britain. We had been supplied with the pistol and ammo but discovered that the ammo was somewhat elderly and perhaps beyond it's use by date. Being so far from places like the coastguard or military who might safely have disposed of same, our illustrious leader decided it should all be fired off. Some worked, some partially misfired by which I mean the flare exited the muzzle at rather less than the desired velocity and some didn't work at all. The latter of course now provided a rather more immediate problem. This problem was rather smartly passed on to the fire service, who had no more clue what to do with misfires than we in ATC did.
Incidentally did you know that french and british verey pistols are of very slightly different calibre, I think 11/2 inch and 38mm. Close but enough to cause a jam if the discrepancy is the wrong way round. I discovered this in the Condominium of the New Hebrides as when I was there the the pistol was supplied by one colonial power and the ammo by the other.