You must be recovering them intact from soft mud or something where they haven't hit anything hard enough to deform/break the plating. An intact plated bullet will NOT allow the molten lead inside it to escape unless the plating is penetrated.
Plated bullets I recover from my club's indoor range have hit an angled steel plate to deflect into the sand trap. They're badly deformed, never intact.
The more people I meet, the more I love my dog
They're going to get their butts kicked over there this election. How come people can't spell and use words correctly?