Why different moving speeds?

Unity Engine
1

Hello!
my projectile is sometimes moving slow, sometimes faster… Why?
The same problem has the firerate time, too.

using System.Collections;
using UnityEngine;
using UnityEngine.UI;

public class ControlPlayer : MonoBehaviour
{
    protected Joystick joystick;
    protected JoyButton joybutton;
    public GameObject bullet;
    public GameObject weapon;
    float bulletSpeed = Global.StandardGunBulletSpeed;
    public float fireCoalDown = 0.1f;
    float fireRate = Global.standardGunCoolDown;
    float nextFire;
    GameObject bulletClone;

    // Test shooting via RayCast
    public float damage = 20;
    public float range = 100;

    // Engine Particles
    public GameObject engine1;
    public GameObject engine2;

    void Start()
    {
        joystick = FindObjectOfType<Joystick>();
        joybutton = FindObjectOfType<JoyButton>();
        nextFire = Time.time + fireRate;

    }
 

    // Update is called once per frame
    void Update()
    {
        Camera.main.transform.position = new Vector3(transform.position.x, transform.position.y, Camera.main.transform.position.z);



        var rigidbody = GetComponent<Rigidbody2D>();

        rigidbody.velocity = new Vector2(joystick.Horizontal * Global.playerSpeed * Time.deltaTime,
            joystick.Vertical * Global.playerSpeed * Time.deltaTime);

        if (joystick.Vertical != 0 && joystick.Horizontal != 0)
        {
            Vector2 v = rigidbody.velocity;
            float angle = Mathf.Atan2(v.y, v.x) * Mathf.Rad2Deg;
            Quaternion endRotation = Quaternion.AngleAxis(angle, Vector3.forward);
            Quaternion startRotation = transform.rotation;
            transform.rotation = Quaternion.Lerp(startRotation, endRotation, 7f * Time.deltaTime);

            if (!engine1.GetComponentInChildren<ParticleSystem>().isPlaying)
            {
                engine1.GetComponentInChildren<ParticleSystem>().Play();
            }
            if (!engine2.GetComponentInChildren<ParticleSystem>().isPlaying)
            {
                engine2.GetComponentInChildren<ParticleSystem>().Play();
            }
                
        }


        if (joybutton.pressed && Time.time >= nextFire)
        {

            nextFire = Time.time + fireRate;
            fire();


        }




    }

    public void fire()  {
             


        RaycastHit2D hit = Physics2D.Raycast(weapon.transform.position, transform.right, 5);
        if (hit.collider != null && hit.collider.name != "Background") {
            if (Vector2.Distance (hit.point, weapon.transform.position) <= Global.StandardGunRange) {
                bulletClone = bullet;
                Vector3 position = (weapon.transform.position);
                bulletClone = (GameObject)Instantiate (bulletClone, position, weapon.transform.rotation);
                bulletClone.GetComponent<Rigidbody2D> ().AddForce (weapon.transform.right *  bulletSpeed * Time.deltaTime, ForceMode2D.Impulse);

            }

        }


    }

}
2

Rigidbody.velocity already takes Time.deltaTime into consideration, so you should not multiply by Time.deltaTime when setting the value of Rigidbody.velocity in your Update().

Every frame, rigidbody basically runs this code in the background (plus some additional physics):

transform.position += rigidbody.velocity * Time.deltaTime;