Requirements: 4 Players
Average Completion Time: 35+ Minutes
Things NOT to be done:
1- Do NOT Die
2- After the Drill opens the gate door to the vault hallway with the elevators DO NOT destroy any cameras after the gate, Until the drill is planted on the secret door
3-Do not plant all C4 on escape wall while waiting for the drill to complete.

Note: Can be Done on "Easy" difficulty
Tutorial to achieve overdrill:

1.Ok, so for the first half of the mission continue as normal. After opening the first gate with the drill make your way into the next room and take out the guards.(don't Destroy any cameras)

2.Plant thermite and go back to hallway with the elevators.

3.Have each of the 4 players stand in these postions
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4.Do Not move untill the orange out line of the drill appears above the vault. (It should appear after you hear a few beeps, and the door wont be there before this is done)

5. Next wait untill the main vault opens, have 2 clean it out while the rest guard the hallway with elevators.

6.One person go to the wall where you plant c4 and plant 2 of the 3 charges. This will prevent guards from spawning in the elevator.

7.All people should remain in the Hallway with the elevators untill the door is open. It'll take around 25-30 minutes

8.When the secret door opens one person must go in and enter this code using the tiles on the floor
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9. When Vault Opens grab loot and escape!

This process will gain you some serious EXP and even a santa hat (Grab the present) Rank 9 would become 38 at the end of this.
So Good luck with this and remember DON'T DIE!