Heres a video I threw together so people can see how to view hitboxes and edit them if so desired, I'm currently working to fix all the TTT hitboxes for highwon but someone could always feel like editting the deathrun models or anything else.
Standing right next to someone and shooting them in the head with a colt only for blood to kinda come out really rustles my jimmies
Highwon has agreed to let me fix hitboxes for the models just right now he doesn't have time to add them he's waiting until later in the month.
I noticed something with the hitboxes. I once started shooting an afk with the Tron playermodel in the head but it didn't register any shots. Curious, I shot to the side of the head, and the hit registered! It looks like there is an issue where the hitbox doesn't align with the player model which can explain getting shot behind walls and the infamous headshot bug.
If you see blood, that means you hit the hitbox, but it didn't register server side, if you don't hit the hitbox there's no blood at all, which is mostly the case with some Trouble in Terrorist Town models and alot of Deathrun models
You can hit the head hit-box, have it show blood, but have it not register server-side, there's a hit-box issue (with some custom models on SGM), and a hit-reg issue (The game itself).
If its something you downloaded on your own it goes into your addons folder as a compressed file with only a number as a name (its the workshops addon id) or if it downloads from a server it goes to \GarrysMod\garrysmod\download\models or to addons.