Camera clipping through gun when looking down sight.

Example:

I’m animating all the gun movements using a simple IK rig. My first question, how do you go about making an accurate camera setup in maya to animate the FPS gun movements (walk, idle, run, looking down the sights) so that the gun remains in the same place in UE camera after import.

Second question is - how do you deal with the camera clipping through the gum model when using the iron sight?