Hello.
If you watch this at 0.25x speed you'll notice the mercs moving in tandem with gunfire from a sentry gun, with Scout seemingly even moving slightly faster.
But how fast does Sentry Fire move?
That's easy.
Level 3 Sentry Guns have two Gatling Guns mounted on top of them, which fire at 800 m/s or Mach 2.33236152 at the very least, which is Supersonic. Level 1 and Level 3 Sentries fire at the same speeds, therefore it's fine to scale the Level 1 variant to the Level 3 one in this regard.
Note that TF2's universe has consistently been shown to be technologically far superior to the real world (take this for instance), so they likely scale even higher than this.
Movement speed
Scout's in-game speed: 400 hammerunits;
400 hammerunits equal to 800 meters per second.
800 / 400 = 2
1 hammerunit equals to 2 meters per second.
Scout: 400 HU/s -> 800 m/s or Mach 2.33236152; Supersonic
Soldier: 240 HU/s -> 460 m/s or Mach 1.39941691; Supersonic
Pyro: 300 HU/s -> 600 m/s or Mach 1.74927114; Supersonic
Demoman: 280 HU/s -> 560 m/s or Mach 1.63265306; Supersonic
- Demoknight's charge: 750 HU/s -> 1500 m/s or Mach 4.37317784; Supersonic+
Heavy: 230 HU/s -> 460 m/s or Mach 1.34110787; Supersonic
Engineer: 300 HU/s -> 600 m/s or Mach 1.74927114; Supersonic
Medic: 320 HU/s -> 640 m/s or Mach 1.86588921; Supersonic
Sniper: 300 HU/s -> 600 m/s or Mach Mach 1.74927114; Supersonic
Spy: 320 HU/s -> 640 m/s or Mach 1.86588921; Supersonic
This is a bit of a lowball given that mercs such as Soldier appear to have moved in tandem with the Sentry Fire, too.The upgrades boosts the movement of the mercs by 30%.
Scout: 520 HU/s -> 1040 m/s or Mach 3.03206997; Supersonic
Soldier: 312 HU/s -> 624 m/s or Mach 1.81924198; Supersonic
Pyro: 390 HU/s -> 780 m/s or Mach 2.27405248; Supersonic
Demoman: 364 HU/s -> 728 m/s or Mach 2.12244898; Supersonic
- Demoknight's charge: 975 HU/s -> 1950 m/s or Mach 5.6851312; Hypersonic
Heavy: 299 HU/s -> 598 m/s or Mach 1.74344023; Supersonic
Engineer: 390 HU/s -> 780 m/s or Mach 2.27405248; Supersonic
Medic: 416 HU/s -> 832 m/s or Mach 2.42565598; Supersonic
Sniper: 390 HU/s -> 780 m/s or Mach Mach 2.27405248; Supersonic
Spy: 416 HU/s -> 832 m/s or Mach 2.42565598; Supersonic
Reactions / Combat speed
Scout can throw the Flying Guillotine at 3000 hammerunits per second, which equals to 6000 m/s or Mach 17.4927114, which is High Hypersonic, nearing High Hypersonic+.
All of the mercs are consistently able to react to and engage in combat with Scouts, so this scales to all of them. Scout is just the fastest in terms of movement speed.
Thanks to the upgrades, Scout can now throw it at 4800 hammerunits per second.
(17.4927114/3000) * 4800 = 27.9883382
Mach 27.9883382 is Massively Hypersonic.
Thanks for reading.