How can you properly read JSONs in Unity?

Question

So, for my game I would like to be able to add new projectiles easily by reading a JSON file and it just isn't working for me. I've never really used JSON before so I'm new to it and I just keep confusing myself. Here is the code and an example of the JSON I'm working with (N.B. I'm working in C#):

public class JSONTest : MonoBehaviour {
{
    [Serializable]
    public class Root
    {
        public Projectile[] proj;
    }

    [Serializable]
    public class Projectile {
        public int ID;
        public string name;
        public float velocity;
        public int bounces;
        public bool explosive;
    }
    public static Root JsonConvert(string Json)
    {
        return JsonUtility.FromJson<Root>(Json);
    }
}

// Start is called before the first frame update
void Start()
{
    string jsonString = File.ReadAllText(Application.dataPath + "/JSON/Projectiles.json"); //reads the file into string
    Debug.Log(jsonString);
    Root test = Projectile.JsonConvert(jsonString);
    Debug.Log(test.proj.Length);
}

}

JSON:

{
    "Projectiles":[{    
        "ID":1,
        "name":"Bullet",
        "velocity":1.5,
        "bounces":3,
        "explosive":false
    }, {
        "ID":2,
        "name":"Rocket",
        "velocity":3,
        "bounces":1,
        "explosive":true
    }]
}

Every time it runs, I get a NullReferenceException on the second Debug.Log().

Any help would be greatly appreciated