RayViewer.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class RayViewer : MonoBehaviour
{
    public float weaponRange = 50f;
    private Camera fpsCam;


    void Start()
    {
        fpsCam = GetComponentInParent<Camera> ();
    }

    
    void Update()
    {
        Vector3 lineOrigin = fpsCam.ViewportToWorldPoint(new Vector3(0.5f, 05f, 0));
        Debug.DrawRay(lineOrigin, fpsCam.transform.forward * weaponRange, Color.green);
    }
}