TY guys.
If I miss when firing on heavy its 90% low FPS. I tend to not miss heavies with ~20-30FPS. Also Deatgbane told me missiles are hardcoded to always be set on high settings. Why? Lots if missiles (and certain maps mainly inferno and clearcut) eat my FPS like a pack of hungry wolves. (insta ~20 to ~10)
For each detail level, you need a different particle.
For example, explosion effects on inferno. These should have 3 particles for the same effect, low medium and high.
Currently only one particle, high, is placed on the map. Since the other two dont exist, when you scale down your settings, the particle effect remains on high due to the other two particles not existing.
Thats the best i can explain it right now, quite tired.