I have used a lot of military ammo for 303s and to avoid the use of the
Fulminate of Mercury primers I pull the bullet and empty the cases,
I then throw the cases in a pot of boiling water for 20 minutes which makes the
primers inert and then remove them by the hydraulic method.
They have to be removed before the primers have dried out again as they
are active once more when dry.
Boiling them is an extra safety, It is time consuming but if you want
clean cases it is worth the time