Storing camera angles for a FPS

I am making a First Person Shooter as sort of an introduction to programming.
I have separate scripts. one handles movement and camera rotation, one handles spawning the bullets and applying a force to them, and the last handles specifics of shooting a bullet.

However, I would like to make it so whenever a bullet is instantiated, the camera rotates simulating knock-back in a way; but I’m not quite sure how to do that. Here is my code:

void Update () {
	Quaternion x = Quaternion.Euler (Input.GetAxis ("Mouse X"));
	Quaternion y = Quaternion.Euler (Input.GetAxis ("Mouse Y" + 3));
	if(Input.GetButton ("Fire1")){
		Camera c = Camera.main;
		verticalRotation = Input.GetAxis ("Mouse Y");
		c.transform.localRotation.Quaternion.Euler(x,y,0);
	}

}

In this, I’m trying to store the camera rotation in Quaternion angles, and add 3 to the camera’s vertical rotation nudging it up a bit. Is this a viable way of doing such a thing and I’m just missing something, or should I go a completely different route?

This method gets a little bit jittery so what I do is parent the main camera to an empty GameObject. Use that gameObject as the “camera” for your character camera script and then use the actual camera to handle all extraneous camera motions.