That is what it's capped at...30 FPS [as Sajuuk said]. That's so we could watch it at a normal framerate on your stream. If you've ever looked at an AVI or DivX file you notice their framerate is 29.97 or 25. That's why you're capped.Try recording in FRAPs @ 60 FPS and play it back...it's twice the speed you did things at. If you record @ 30 FPS and play it back it looks completely normal even though in game you notice the 'choppy-ness'.

http://en.wikipedia.org/wiki/29.97