- "Our staple ammo was the NATO 5.56 Cherry PIE. PIE stands for Pyrotechnically Initiated Explosive. Outstanding design. It would shatter on entry into Zack's skull and fragments would fry its brain. No risk of spreading infected gray matter and no need for wasteful bonfires. On BS duty, you didn't have to decap before you buried them, just dig the trench and roll the whole body in."
- — Todd Wainio's description of the PIE round.
The NATO 5.56 PIE cartridge (also known as a Cherry PIE round) was the staple cartridge in the reclamation of North America from the Zombie Horde in World War Z. Usually fired from the Standard Infantry Rifle, the Pyrotechnically Initiated Explosive round was designed to inflict maximum damage by superheating and exploding after striking its target. Partial headshots and neckshots to zombies became killshots as the area around the wound would burn up and explode. The Cherry Pie nickname is drawn from the reddish fiery glow that sometimes emanated from the orifices of the zombie skull when the round entered the head. According to Todd Wainio, the glowing eyes were a "cure for constipation".