how to practice aiming at long range?

I'm a k2 user and I've been trying to pull my headshot ratio up higher. I've been having problems h/sing at longer range tho.

I can get close and it looks like its on mark a lot but the shots will hit there neck, chest.
CF is my first fps game so I don't know what kind of practice you would do to be more accurate at range (without a scope) does anyone know of anything like that?

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