Projectiles Stop in mid air

Hello, here is a script that is suppose to send out a projectile in the air untill gravity takes care of it (rigidbody). But my projectiles stop in mid air in front of me. What did i do wrong?

using UnityEngine;
using System.Collections;

public class FireProjectile : MonoBehaviour {
	
	public GameObject projectilePrefab;
	public float Speed;
	
	// Use this for initialization
	void Start () 
	{
		if(projectilePrefab == null)
		{
			Debug.Log("bullet object is null. Please set a GameObject into the bullet type");
			Debug.Break();
		}
	}
	
	// Update is called once per frame
	void Update () 
	{
		if(Input.GetButtonDown("Fire1"))
		{
			Instantiate(projectilePrefab, transform.position + transform.forward * Speed, transform.rotation);
		}
	}
}

I don’t think you should add all of that to just Instantiate. What you should do is add the AddForce function after.

using UnityEngine;
using System.Collections;

public class FireProjectile : MonoBehaviour {
	
	public GameObject projectilePrefab;
	public float Speed;
	
	// Use this for initialization
	void Start () 
	{
		if(projectilePrefab == null)
		{
			Debug.Log("bullet object is null. Please set a GameObject into the bullet type");
			Debug.Break();
		}
	}
	
	// Update is called once per frame
	void Update () 
	{
		if(Input.GetButtonDown("Fire1"))
		{
			GameObject projectile = (GameObject) Instantiate(projectilePrefab, transform.position, transform.rotation);
			projectile.GetComponent<Rigidbody>().AddForce(transform.forward * Speed);
		}
	}
}

The speed needs to be really high. Set it to 1000 and tweak it from there.