I was looking around some sites and found this
1. Be a level 50 in "Combat Training".
2. Switch the lobby to "Player Match".
3. Have a friend setup a "Player Match" lobby and invite you (accept the invite).
4. Have the friend switch the lobby to "Combat training" and then switch it back to "Player Match".
5. Once in "Player Match", hit "Playercard", then "Edit Playercard".
6. Stay in the "Edit Playercard" menu, and have your friend switch the lobby to "Combat Training".
7. Hit "B', then "Do Not Save", then prestige.
8. After you have prestiged leave the menus up and have your friend turn off his Xbox.
9. After a few seconds it will say your friend has left and you will be in a "Player Match" lobby.
10. You will now be the same rank you just prestiged to.
Example: You are a 14th prestige lvl 50 in CT, you do this glitch and prestige.. You will now be lvl 15th prestige lvl in the player match loby.
Now the only problem is that if you go to the main menu it will go away, and it wont let you start a player match.
I haven't been able to test on this much, but I'm sure you guys will find a way to make this permanent.
*I've noticed that if you do this glitch and have "Load Multiplayer By Default" enabled, it disables it