Reflected grenades, sentry rockets, and detonator flares deal 85-170 self-damage. Normally, grenades deal 37.5-75 self-damage, sentry rockets deal 50-100 self-damage, and detonator flares deal 15-30 self-damage (22.5-45 with item penalty).
This happens because they use the flamethrower's "Damage" value of 170 (which is approximately equal to max flamethrower dps). Editing this value does not change the flamethrower's damage, but it changes the self-damage for these reflected projectiles.
From scripts/tf_weapon_flamethrower.ctx:
"Damage" "170" // per second
The Dragon's Fury is also affected by this bug, but it will deal a lot less self-damage. Reflected grenades, sentry rockets, and detonator flares deal 45-90 self-damage. This is because its "Damage" value is 90, which also does not change the weapon's actual damage when edited, but changes the damage for reflected projectiles.
From scripts/tf_weapon_rocketlauncher_fireball.ctx:
"Damage" "90"
Reflected rocket launcher rockets are unaffected so they correctly deal the normal 45-90 self-damage. Reflected rockets from Liberty Launcher, Air Strike, and Rocket Jumper deal 75%, 85%, and 0% self-damage respectively, so their item bonuses all behave correctly.
Splash radius is unaffected by this bug, so reflected explosives still use their correct self-damage radius: 146 Hu for grenades, 121 for rockets, and 100 for flares.
Reflected grenades, sentry rockets, and detonator flares deal 85-170 self-damage. Normally, grenades deal 37.5-75 self-damage, sentry rockets deal 50-100 self-damage, and detonator flares deal 15-30 self-damage (22.5-45 with item penalty).
This happens because they use the flamethrower's "Damage" value of 170 (which is approximately equal to max flamethrower dps). Editing this value does not change the flamethrower's damage, but it changes the self-damage for these reflected projectiles.
From scripts/tf_weapon_flamethrower.ctx: "Damage" "170" // per second
The Dragon's Fury is also affected by this bug, but it will deal a lot less self-damage. Reflected grenades, sentry rockets, and detonator flares deal 45-90 self-damage. This is because its "Damage" value is 90, which also does not change the weapon's actual damage when edited, but changes the damage for reflected projectiles.
From scripts/tf_weapon_rocketlauncher_fireball.ctx: "Damage" "90"
Reflected rocket launcher rockets are unaffected so they correctly deal the normal 45-90 self-damage. Reflected rockets from Liberty Launcher, Air Strike, and Rocket Jumper deal 75%, 85%, and 0% self-damage respectively, so their item bonuses all behave correctly.
Splash radius is unaffected by this bug, so reflected explosives still use their correct self-damage radius: 146 Hu for grenades, 121 for rockets, and 100 for flares.
There already seems to be a community fix present for this problem https://github.com/ldesgoui/tf2-comp-fixes
Source: https://www.youtube.com/watch?v=cvGbGDuHZaI