TurretController Script Raycast problem

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


public class TurretController : MonoBehaviour
{
    private RaycastHit hit;
    private Transform target, turret;
    public Transform barrel_tip;
    private Vector3 direct;
    public float Speed = 2.0f, range = 30.0f;
    List<Collider> enemy_list;
    private Animator anim;
    Quaternion rot;

    void Start()
    {
        enemy_list = new List<Collider>();
        turret = transform.GetChild(0);
        //barrel_tip = transform.GetChild(1);
        anim = turret.GetComponent<Animator>();

    }
    // Update is called once per frame
    void Update()
    {

        Collider[] colliders = Physics.OverlapSphere(transform.position, 30);
        for (int i = 0; i < colliders.Length; i++)
        {
            if (colliders[i].tag == "Enemy")
            {
                enemy_list.Add(colliders[i]);
            }
        }

        if (enemy_list != null)
        {
            foreach (Collider enemy in enemy_list)
            {
                RotateTurret(enemy);
                Debug.DrawLine(barrel_tip.position, barrel_tip.position + (barrel_tip.forward * range), Color.red);
                if (Physics.Raycast(barrel_tip.position, barrel_tip.transform.forward, out hit, 50))
                {
                    Debug.Log(hit.distance);
                    if (hit.distance < range)
                    {
                        print("Target in range.");
                        anim.SetBool("enemy_det", true);
                    }
                }
            }
        }
        else
            print("Error: enemy_list is NULL.");
    }

    void RotateTurret(Collider col)
    {
        target = col.transform;
        direct = target.position - transform.position;
        direct.y = 0;
        rot = Quaternion.LookRotation(direct);
        transform.rotation = Quaternion.Slerp(transform.rotation, rot, Time.deltaTime * Speed);
    }
}