Server Tickrate

Due to a combination of low the server tick rate is and client prediction can lead to incredibly aggravating results like this.

https://clips.twitch.tv/KathishIntelligentMoosePhilosoraptor the last 4s at 0.25x speed

https://i.imgur.com/GLddTGj.png

^this image is the very last frame before I died. It shows me not only firing the peacekeeper but ALSO a bloodspray on the lifeline. They're dead center of my crosshair with a lot of the pellets having to hit the head, this should've been a kill shot. Lifeline at this point was ~54hp or less. Somehow I did 0 damage. 

This can only mean that projectiles are in fact delayed by Interpolation (directly tied to server tickrate) + client ping as well as the client rendering projectiles you fired before they actually exist in the game world.