I don't want to create another topic for the same reason of this one so:
Bump! :) Here is a copy past of what I said in another forum:
I didn't read the 10 pages, sorry, I don't have the time to do it this evening.
From what I read, some people think the mouse lag is the way bis simulates the weight of the weapon, but, no. You can't talk about something you didn't see, so I invite you to watch my video "http://www.youtube.com/watch?v=xryLypk7I9c"
As you can see, the more details you have, the more mouse lag you'll have. Crappy graphic = almost no mouse lag, beautiful graphic = ... beautiful mouse lag :D
It has NOTHING to do with the FPS guys. I can put very high on crysis (snow part), I'll have something like 15-20 fps, but there will not be any mouse lag, just crappy FPS.
So, if someone finds any solution, I would thanks him for telling me =P
(Ho, and I also tested with no V.Sync, it's the same problem)
Once again, sorry for my bad english.