A fellow Texas racer uses surplus ammo boxes to store his LiPos. Two years ago he had a pack blow while in a closed box - this was a .50 caliber box, pretty heavy. He had a 1/2" hole in the side for charge wires. When the 6S pack went off the box shot across the pit area several feet like a rocket. The steel box contained the 'explosion' and the resulting fire just fine, no melting, no external fires.
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