Well this is most likely due to your ping (how many ms it takes for the server to respond to what you are doing).
I have around 100-150 ping in the pub an up to 200 in the private and sometimes when I die, like when I try to rush in to a room for me I look safe but I have already been killed and that I notice when the killcam comes up and I am on the other side of the dorr.
So I don't think it is something wrong with your configs it is just other people have higher or lower ping than you, so all you need is a littlebit of luck and training. Just remember that if you miss it is not due to that you have a bad aim or that they are cheating it is just the ping most likely.