If Florida bans them, they are a truly deadly weapon system. It would appear that they could even penetrate Kevlar armor.
Armor-piercing or exploding ammunition or dragon’s breath shotgun shells, bolo shells, or flechette shells prohibited.
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(f) “Flechette shell” means any shell that can be fired in a firearm and that expels two or more pieces of fin-stabilized solid metal wire or two or more solid dart-type projectiles.