lag isn't related to fps, in the lobby what is your ping? Do you have packets lost?
How do i check it in the lobby?
I'm on a cell phone right now, but I think clicking on late war arena then show arena details under the list is the way to go.
Im receiving as many as im sending.
I'm amazed you manage 60+ fps with that rig mine is very similar with a slightly better Vid card and I get nowhere near that performance although I play at 1680 x 1050.