Failed to create a gamper

I want to create a barrage using vehicle game tutorial.

The gif represents what my game looks like now.

In the illustration, I explained what I want and the current status.

Actually the difference between 2 and 3 is just a for loop. I wonder why it looks good when I have just 1 layer, while it fails to create so many layers of the 5 bullets in 2?

Here is my Shot() method: private void Shot() { m_Shot = true;

     for (int j = 0; j < m_ShotDirections; j++)
     {
         float direction;
         Vector3 shotDirection;
         for (int i = 0; i < m_ShotTimes; i++)
         {
             if (j < m_ShotDirections / 2)
             {
                 direction = 80 - j * 40;
                 shotDirection = m_FireTransform.forward * (90 - direction) / 90 - m_FireTransform.right * direction / 90;
             }
             else if (j > m_ShotDirections / 2)
             {
                 direction = 80 - (m_ShotDirections - 1 - j) * 40;
                 shotDirection = m_FireTransform.forward * (90 - direction) / 90 + m_FireTransform.right * direction / 90;
             }
             else
             {
                 shotDirection = m_FireTransform.forward;
             }

             Rigidbody shellInstance = Instantiate(m_Shell, m_FireTransform.position, m_FireTransform.rotation) as Rigidbody;


             shellInstance.velocity = m_CurrentLaunchForce * shotDirection;

             m_ShootingAudio.clip = m_FireClip;
             m_ShootingAudio.Play();

             m_CurrentLaunchForce = m_MinLaunchForce;
         }
     }
 }

 private void Nothing()
 {

 }

By the way, does anyone have any idea about how to rotate the shell rigidbody to make it align with the direction it burst out? I have been frustrated with these problems for so long.