Help Adding Local Force and Rotating in a For Loop

I’m making an action platformer and the game play centers around the player shooting a shotgun like this

So I already have the gun shooting singular bullets and dealing damage to enemies what I need help with is two things. The first one is simple here’s my code, I need help adding velocity along a local axis. the next thing is a little bit more difficult, I need to rotate each bullet between the negative and positive value of bulletSpreadAngle. so I can then add the local force along the x axis.

float numOfBullets = 5f;
    float bulletSpeed = 10f;
    float bulletSpreadAngle = 45f; // How far the farthest bullet will be tilted
    GameObject bulletPrefab; // Defined in the editor, this is the prefab that all bullets are spawned from
    void ShootWeapon()
            // bullet's rotation = spread distance / number of bullets
            // Every iteration in the loop add onto the rotation and rotate the bullet that much
            for (int i = 0; i < numOfBullets; i++)
                for (float j = -bulletSpreadAngle; j < bulletSpreadAngle; j += bulletSpreadAngle / numOfBullets)
                    GameObject bullet = Instantiate(bulletPrefab, gunEnd.position, Quaternion.identity);
                    Rigidbody2D projectileRigidbody = bullet.GetComponent<Rigidbody2D>();
                    if (transform.localScale.x > 0)
                        //bullet.transform.rotation = new Quaternion(Quaternion.identity.x, Quaternion.identity.y, Quaternion.identity.z * j, Quaternion.identity.w);
                        projectileRigidbody.velocity = new Vector3( bulletSpeed, projectileRigidbody.velocity.y);
                    else if (transform.localScale.x < 0)
                        projectileRigidbody.velocity = new Vector2(-bulletSpeed, projectileRigidbody.velocity.y);

You can try using Vector3(new Vector3(0,0,0) and Mathf.SmoothDamp and Mathf.Lerp. Check it on Unity API!

Sine and cosine will do the job:

projectileRigidbody.velocity = new Vector2(
) * bulletSpeed;