Help with no aiming kills:).

How to increase my effectiveness with no aim killing...
For example,when im in 1on1 close battle with rifles,snipes. it's happened so frequently that i'm sure that cross of weapon stops right somewhere on opponent chest, and then i fire, but nothing...ok i'm thinking its only one bullet, but then i fire another bullet,and im sure that again i was accurate, definitely hit him...but again nothing...
It's happening so many times...i dont get it.
Where is problem...i usually dont use configs, its that problem, or something other.
Or my ping is high, usually at 60,sometimes goes to 70,80...but i doubt it.

Try to crouch or prone to get a smaller x-hair.

Also, the less you move, the smaller the x-hair will be so try and move less to get better accuracy (or move really quick, then stop, get the small x-hair, shoot, then move quickly again)  

no need for changing fps and stuff