Calculation, based on Episode 23 which is pretty simple:
From 9:10 to 9:15 it take 4,48 second for projection to hit the moon
Chariot hit moon in 4,48 second, which mean that her shot take 384403 km from Earth to Moon whith speed 85804 km/s which are 250157 mach and it give her 28% from SoL for Attack Speed with Shiny Arc only, which also should be acceptable for Akko' attack speed with Shiny Arc too.
So, end result is Relativistic