From Team Fortress Wiki
Hitscan attacks instantly damage targets in their path. All hitscan attacks emit down the crosshair, from the attacker's eye level, despite what is suggested by the view model and world model. Unlike projectiles, hitscan attacks are not code-rendered physical objects but are infinitely-thin lines drawn on the server that are then rendered client-side visually as projectiles. Depending on the object hit and client settings, the hitscan weapon then generates an effect: dealing damage or painting blood and bullet hole sprites.
In technical terms, this means that hitscan weapons have infinite velocity, but this does not mean that they always damage instantly after firing.
Melee weapons, with the exception of the Spy's unique melee weapons and the Engineer's melees while working on a building wait 0.25 seconds after input before initiating a short-ranged hitscan attack. This prevents the weapon from hitting or killing a foe before the melee animation completes.
There are two main types of hitscan attacks: those that make contact with the bullet-based hitbox (the eponymous 'bullets' and the Showdown taunt attack) and those that make contact with the environmental/projectile hitbox (melee weapons, the Chargin' Targe bash, and most other taunt attacks).
Bullet-based weapons (a list of which is given below) fire infinite lines. When fixed weapon spread is disabled, all bullet-based weapons (with the exception of the Ambassador) are affected by bullet-spread during a 1.25 second cooldown after firing a bullet, which causes bullets to move off-course to varying degrees. The Ambassador is the sole exception to this rule, and can fire a perfectly-accurate shot after a 0.8 second cooldown. Weapons that fire multiple pellets, like the Shotgun and Scout primaries guarantee a pellet straight down the crosshair if the weapon was not fired within the last 1.25 seconds. When fixed weapon spread is enabled, these weapons that fire multiple pellets will use a fixed spread pattern that does not require a cooldown to be accurate. For example, the Shotgun uses a fixed 3x3 pattern when fixed spreads are enabled. If a weapon fires more than 9 pellets at once, fixed spread will cause multiple pellets to hit the same location.
Hitscan weapons have the ability to destroy enemy stickybombs once they're attached to a surface.
|List of bullet-based hitscan weapons|
|Scattergun||Force-A-Nature||Shortstop||Soda Popper||Baby Face's Blaster|
|Pistol||Lugermorph||Winger||Pretty Boy's Pocket Pistol|
|Minigun||Natascha||Iron Curtain||Brass Beast||Tomislav||Huo-Long Heater|
|Sentry Gun||Combat Mini-Sentry Gun|
|Sniper Rifle||Sydney Sleeper||Bazaar Bargain||Machina||Hitman's Heatmaker||AWPer Hand|
|Submachine Gun||Cleaner's Carbine|
The following is a model-by-model video rendering of the bullet-based hitboxes:
- Hitscan on the