public class NewBehaviourScript : MonoBehaviour {

    public Transform bullet;
    public int BulletForce = 5000;
    public int Magaz = 15;

    void Update () {
        if (Input.GetMouseButtonDown(0) && Magaz > 0) {
            Transform BulletInstance = Instantiate(bullet, GameObject.Find("spawn").transform.position, Quaternion.identity);
            BulletInstance.GetComponent<Rigidbody>().AddForce(transform.forward * BulletForce);
            Magaz -= 1;
        }
        if (Input.GetKeyDown(KeyCode.R)) {
            Magaz = 15;
        }
    }
}