although i never watched a mythbusters episode after googling will a tank explode when shoot i learned that on episode 115 it will infact not explode
REVISITED: A gas tank will explode when shot by a bullet. (From Episode 15)
busted
It has already been proven that when shot by a normal bullet a gasoline tank will not explode. However, if a gasoline tank is shot by a tracer round from a great enough distance so that the round can ignite with air friction, it will cause the gasoline to catch fire. By the time this happened the tank was so riddled with bullets (from previous tracers that were fired too close to ignite) that there was no contained pressure, but the MythBusters surmised that had the tank been properly enclosed, it may have exploded; but overall it remains extremely improbable.