Bullet spread headshots etc.

How do some of these people have like it seems no bullets spread? I shoot at them they turn around and boom 3 headshots instantly they move around like crazy, its like it doesnt even change thier spread even though it should. They have super duper accuracy. And also have a weird rpm almost like bursts but with 0 delay that speads up their gun. Is this what makes them have no bullet spread.

Just a question. And if in the case yall have any tips for gunplay I would like to know thx