Twin Stick Shooter controller

Hi,

I'm learning Unity and C#.

I try to make a Twin stick shooter game using the left and right Thumbstick of my Xbox pad. My character move correctly on the x and z axis. But the rotation of the gun on the y axis is not working correctly, it get stuck in Angles. I can't have a smooth rotation..

 using UnityEngine;
 using System.Collections;

 CharacterMotor controller;

 public Transform player_turret;
 public float deadzone = 0.25f;

 private Quaternion desireRotation;
 void  Update (){
 CharacterController controller = GetComponent<CharacterController>();
 moveDirection = new Vector3(Input.GetAxis("Horizontal")*speed*Time.deltaTime, 0, Input.GetAxis("Vertical")*speed*Time.deltaTime);
 moveDirection = transform.TransformDirection(moveDirection);
 controller.Move(moveDirection);
 
 //right stick dead zone
 Vector2 shootDirection = new Vector2(Input.GetAxis("FireHorizontal"), Input.GetAxis("FireVertical"));
 if(shootDirection.magnitude < deadzone){
 shootDirection = Vector2.zero;
 }else
 {
 Vector3 shootRotation = new Vector3(shootDirection.x, 0, shootDirection.y);
     desireRotation = Quaternion.LookRotation(shootRotation);
     player_turret.rotation = desireRotation;
 if((Time.time >= nextFireTime) && Input.GetButton("Button A")){
         FireProjectile();
     }
 }
 }

Thank you for your help :)