Set up a private match and make sure old school is turned on (Note: you will need 2 people for this).
when you loaded ambush be opfor.
Then as soon as you spawn there should be a wall on the left side.
Go to that wall and have 1 person go prone on the left corner of the wall.
Then the other person go as far back as you want and try jumping on top of the person who is proning.
Keep on jumping forward until you are out of the map.
If you want me to help you do this glitch my gamertag is seaQuest12.