I figured it out and I don't like it. Every Weapon has a Core Headshot Damage multiplier. And guess what. Snipers have 0% without they're passive. While a pistol without any Headshot Damage has 100% Headshot Damage, LMG 65%, AR 55%, Rifle 60%, SMG 50% and Shotgun 45%. I don't understand why the need for different core Headshot Multiplier, but giving the Sniper 0% is weird and explains a lot.