Hey guys I'm sure that this is already posted but there are a lot of people who don't know how to do this so I'm gonna tell you how. I know this is old and not new but I'm just trying to help out the community.
Here is how you do it:

1. Invite a friend to a private match.
2. Make the game search and destroy and map on Nuketown.
3. Click on switch lobby.
4. Hover over combat training.
5. Quickly press A Up A. This will start game.
6. It should say team deathmatch on Array.
7. While it is loading you go to xbox dashboard.
8. When the game is done loading it will end and your friend will be in a search and destroy game on Nuketown in combat training.
9. Have your friend invite you back and play as long as you want.

Hope you guys enjoy. Like I said didn't discover this glitch it isn't patched yet I'm playing it right now and I'm sorry if you have already posted this not trying to steal anyones idea. If you need help message TransitionaI (last letter is a capital i not an l)