Tutorial Script: BulletManager

using UnityEngine;
using System.Collections;

public class BulletManager : MonoBehaviour
{
    public MPPlayer shooterPlayer;
    public float destroyTimer = 5;
    public float damage = 0;

    void Start()
    {
        Destroy(gameObject, destroyTimer);
    }

    void OnCollisionEnter(Collision col)
    {
        col.transform.SendMessageUpwards("GetBulletDamage", damage, SendMessageOptions.DontRequireReceiver);
        Destroy(gameObject);
    }
}