Machine Gun shooting

Hello!
I have the TankShooting Script from the Tanks! Tutorial and I need help converting it into a script where when you hold the fire button, it doesn’t recharge but constantly shoots, like a machine gun. I’m using the TankShooting script on all my guns, but they only fire one shot at a time.

Here is the script:

using UnityEngine;
using UnityEngine.UI;
using UnityEngine;
using UnityEngine.UI;

public class TankShooting1 : MonoBehaviour
{
	public int m_PlayerNumber = 1;              // Used to identify the different players.
	public Rigidbody m_Shell;                   // Prefab of the shell.
	public Transform m_FireTransform;           // A child of the tank where the shells are spawned.
	public Slider m_AimSlider;                  // A child of the tank that displays the current launch force.
	public AudioSource m_ShootingAudio;         // Reference to the audio source used to play the shooting audio. NB: different to the movement audio source.
	public AudioClip m_ChargingClip;            // Audio that plays when each shot is charging up.
	public AudioClip m_FireClip;                // Audio that plays when each shot is fired.
	public float m_MinLaunchForce = 15f;        // The force given to the shell if the fire button is not held.
	public float m_MaxLaunchForce = 30f;        // The force given to the shell if the fire button is held for the max charge time.
	public float m_MaxChargeTime = 0.75f;       // How long the shell can charge for before it is fired at max force.




	private string m_FireButton;                // The input axis that is used for launching shells.
	private float m_CurrentLaunchForce;         // The force that will be given to the shell when the fire button is released.
	private float m_ChargeSpeed;                // How fast the launch force increases, based on the max charge time.
	private bool m_Fired;                       // Whether or not the shell has been launched with this button press.


	private void Start ()
	{
		// The fire axis is based on the player number.
		m_FireButton = "Fire" + m_PlayerNumber;

		// The rate that the launch force charges up is the range of possible forces by the max charge time.
		m_ChargeSpeed = (m_MaxLaunchForce - m_MinLaunchForce) / m_MaxChargeTime;
	}


	private void Update ()
	{
		// The slider should have a default value of the minimum launch force.
		m_AimSlider.value = m_MinLaunchForce;

		// If the max force has been exceeded and the shell hasn't yet been launched...
		if (m_CurrentLaunchForce >= m_MaxLaunchForce && !m_Fired)
		{
			// ... use the max force and launch the shell.
			m_CurrentLaunchForce = m_MaxLaunchForce;
			Fire ();
		}
		// Otherwise, if the fire button has just started being pressed...
		else if (Input.GetButtonDown (m_FireButton))
		{
			// ... reset the fired flag and reset the launch force.
			m_Fired = false;
			m_CurrentLaunchForce = m_MinLaunchForce;

			// Change the clip to the charging clip and start it playing.
			m_ShootingAudio.clip = m_ChargingClip;
			m_ShootingAudio.Play ();
		}
		// Otherwise, if the fire button is being held and the shell hasn't been launched yet...
		else if (Input.GetButton (m_FireButton) && !m_Fired)
		{
			// Increment the launch force and update the slider.
			m_CurrentLaunchForce += m_ChargeSpeed * Time.deltaTime;

			m_AimSlider.value = m_CurrentLaunchForce;
		}
		// Otherwise, if the fire button is released and the shell hasn't been launched yet...
		else if (Input.GetButtonUp (m_FireButton) && !m_Fired)
		{
			// ... launch the shell.
			Fire ();
		}
	}


	private void Fire ()
	{
		// Set the fired flag so only Fire is only called once.
		m_Fired = true;

		// Create an instance of the shell and store a reference to it's rigidbody.
		Rigidbody shellInstance =
			Instantiate (m_Shell, m_FireTransform.position, m_FireTransform.rotation) as Rigidbody;

		// Set the shell's velocity to the launch force in the fire position's forward direction.
		shellInstance.velocity = m_CurrentLaunchForce * m_FireTransform.forward;
		;

		// Change the clip to the firing clip and play it.
		m_ShootingAudio.clip = m_FireClip;
		m_ShootingAudio.Play ();

		// Reset the launch force.  This is a precaution in case of missing button events.
		m_CurrentLaunchForce = m_MinLaunchForce;

	}
}

Any help is appreciated!

To do this you can replace

Input.GetButtonDown()

with

Input.GetButton()

Hope this helps!