I've taken this idea, replaced the round nosed softwood sabot with a pointed oak sabot, and replaced the lead shot with silver casting grain (small balls of silver intended to be melted down and made into jewelry, available from Rio Grande jewelers' supplies). Thus far, it has proven very effective against werewolves and vampires, as well as against the stubborn hybrid creature that results when a werewolf bites a vampire, or vice versa.
Interestingly enough, in my state, a werewolf is considered a non-native canid, and can be shot anytime with a valid hunting license, as long as it's in wolf form when you shoot it. A vampire, however, must invade your house before you can legally shoot it under the castle doctrine, and yet vampires won't come into your house unless you invite them. so that's tricky.