For any TrackIR user who has tried using the standard snap key as a gunsight, and failed miserably:

You cannot use "Head: snap center" (NP 5) as a snap key while TrackIR is active. I does not work as a snap key while TrackIR is active, it only recenters your view for a second until TrackIR overrides the snap and your view drifts off center.

BUT YOU CAN USE ANY OTHER SNAP KEY AS A GUNSIGHT, just modify the view using the "remember" key. These other snap keys do not have the "drift" problem with TrackIR.

It is very confusing and unfortunate that "Head: snap center", which is NP 5, CANNOT BE USED LIKE THE OTHER SNAP KEYS while TrackIR is active, because that is the key most people will try to use as a gunsight.

Thanks especially to Brummer for helping me think this through.