There are two spec ops missions you can do in less then 20 seconds, and its kind of easy to do it. The first one is body count. When you spawn, switch out your M9 for the RPG and hop over the fence. Immediatly run to the right and you will see a troop transport truck. Throw a sticky grenade (LeftBumper) on the truck to explode it and kill everyone inside. You will get a x10 combo, and while the points are racking up, use your RPG on one of the BTR80s. The points will rack up quickly and the level will end. My best time is 14.60 seconds, but the best time on record is 5.7 seconds. NOTE: You must destroy the BTR80 while the x10 combo from the truck is racking up or it will not work.

The second speed run mission is breach and clear. This may not seem like a speed run mission, but its alot easier than it looks. Before breaching grab the A12 auto shotty instead of ur secondary weapon. During the slow mo breach, take out the guy flying backwards and the guy immediatly to your left. Switch to your other gun and sprint to the right past the lockers. Keep going and if a guy sticks u to a wall knife him quickly. Once you get to the riot shield soldiers run left and keep going until you reach the hole. My best time is around 15 seconds, but ive seen guys do it in 7 secs. Good luck!