GlyphGryph, you don’t understand how it works at all.
Your base Headshot chance is 25%. Headhunter adds 10%. 25 + 10 and so on.
1st hit to body – 25% chance to hit head.
2nd hit to body – 35% cnance to hit head.
3rd hit to body – 45% chance to hit head.
4th hit to body – 55% chance to hit head.
5th hit to body – 65% chance to hit head.
6th hit to body – 75% chance to hit head.
7th hit to body – 85% chance to hit head.
8th hit to body – 95% chance to hit head.
9th hit to body – he should be already dead anyway.