Get the RPK in one of your classes. Go into any game mode as black ops.

When you first spawn, look behind you and you will see a jeep before the entrance of the bunker.

Go and shoot the bumper off the jeep with the RPK in a three round burst.

It will get off the jeep, start shaking while making crashing sounds and it will keep moving forward for about 10 seconds.

Sometimes it will fly in the air (this also works for some other jeeps).