Freeze Flame (フリーズ・フレイム) is a Speed Type and Oscillation Type Wide Area Magic that can freeze even fire. It is a conceptual magic that prevents anything from burning. This magic can suppress the temperature of targets within a certain threshold.
Although it is said that Magicians are still vulnerable to real fire arms, these still rely on gunpowder, and burning gunpowder to create the force is necessary to propel the bullet. If the flammable object can be prevented from heating up, then ignition would become impossible. Thus, firearms that have been subjected to "Freeze Flame", regardless of whether they are guns or cannons would be silenced so long as they relied on gunpowder or explosives.