mach 3 railgun

She fired the attack that had given her the name Railgun. The coin flew forward at triple
the speed of sound. It heated up as it rubbed against the air and became an orange beam
as it lanced straight through the “tower,” which shattered instantly at the extreme impact.
It and the “head” attached to it all blew into a million pieces.

- Toaru Majutsu no Index Volume 6, Between the Lines 1