- The Air Base Armory is underground at Chang-san Air Base, grid B5–B6 on Hajin.
- You must run Operation Iron Citadel — it gives you objective markers and keeps rival squads away.
- Find the Air Base Access Card inside the base, then upgrade it in the Server Room at Admin Complex No. 2.
- Collect 3 notes inside the bunker to build the randomized six-digit door code.
- Enter the code and swipe the upgraded card to open the Armory vault door.
- Kill the Colossus boss inside, then loot the room — including the DRC Weapons Locker if you have the key.
The Air Base Armory is one of the richest loot rooms in MW4 DMZ. It is buried inside a heavily guarded bunker, but the steps to get in never change. Follow the sequence below and you can clear it on every deployment.
Where Is the Air Base Armory in MW4 DMZ?
The Armory sits underground at Chang-san Air Base in Western Hajin. You enter the bunker through the Entrance Garage on the south side of the base. The Armory itself is in the Air Base Bunker at Tac-Map grid B5–B6.
Pay attention to the threat levels. The Air Base Exterior starts at Critical. Once you upgrade the access card and trigger the base alarm, the entire bunker jumps to Extreme. Bring a strong primary, plenty of plates, and a solid secondary before you drop here. Check out the best assault rifles in MW4 or the best SMGs ranked if you need a loadout before heading in.
Step 1 – Start Operation Iron Citadel
Before anything else, select Operation Iron Citadel when choosing your DMZ mission. This is a Tier 2 Story Mission, so you need to finish all three Tier 1 missions first — Critical Extraction, Silent Ledger, and Shopping Hacks.
Running Iron Citadel matters for two reasons. First, the mission spawns you right outside Chang-san Air Base with active objective markers, so you always know where to go. Second, it is the only way to get the mission access card that opens the Armory vault door. You cannot skip this mission and enter the Armory another way.
You can read more about all DMZ Story Missions and their rewards if you want to plan your progression order first.
Step 2 – Find the Air Base Access Card
Once you are inside Chang-san Air Base, your first job is to find the Air Base Access Card (Multi-Use). This is an Epic key and it is your entry point to the whole sequence.
The card is not in one fixed building. The mission identifies the correct location for you, but there are four buildings near the center of the base where it can appear. Follow your active objective marker and search each building until you find it. Eliminate the guard tower first and push inward — the AI garrison here is dense.
Note: the ordinary Air Base Access Card – Multi Use that sometimes appears as field loot is not the same as the mission card. The DRC Weapons Locker Key also cannot replace it. You need the mission version from Iron Citadel.
Step 3 – Upgrade the Card at Admin Complex No. 2
With the card in hand, head to Admin Complex No. 2 — the large building on the south side of the base. Swipe the card at the back entrance to get inside, then climb the stairs to the Server Room on the upper floor.
Interact with the terminal in the Server Room to upgrade your card. This converts the Epic Multi-Use card into the Airbase Armory Keycard (Single Use) — a Legendary key that is the only thing that opens the Armory vault door.
Warning: upgrading the card triggers the base alarm. Every AI soldier on the base goes on high alert immediately and the threat level climbs to Extreme. Be ready for a heavy push before you reach the bunker entrance.
Step 4 – Enter the Chang-san Air Base Bunker
After the upgrade, move south and enter the Air Base Bunker through the Entrance Garage. Once you are inside, follow the corridor until you reach the Armory Doors. The door reads “Requires Air Base Armory Access Card” and also has a keypad for the six-digit code.
You need both — the card and the code — to open this door. Neither works alone.
Step 5 – Collect All 3 Armory Code Notes
The six-digit Armory code is randomized every deployment. There is no fixed code you can memorize. Instead, you build it from three notes hidden inside the bunker. The notes are called Transfer Slips, and their spawn points are always the same:
- Note 1: Recovery Room — on the reception desk.
- Note 2: Administrative Wing — in the Dining Room to the east.
- Note 3: Security Wing — downstairs on the lower level.
Each note gives you two digits of the six-digit code. Your mission tracker assembles the digits automatically as you collect each one — you can see the running tally labeled Known Digits on your HUD. Once all three notes are collected, the full code appears on your tracker. Use that code at the Armory keypad. Do not rely on a code from a video or a previous run — it changes every match.
Need help navigating the bunker? See our guide on all silo bunker locations in MW4 DMZ and the full DMZ keys and locations guide.
Step 6 – Enter the Code and Open the Armory Vault Door
Return to the Armory Doors. Walk up to the keypad and select ENTER ACCESS CODE. Input the six digits shown on your mission tracker. Then move to the card reader on the right side of the door and swipe the Airbase Armory Keycard.
Both requirements — code and card — must be satisfied for the vault door to open. If the door is not opening, double-check that you upgraded the card in the Server Room and not just using the standard Multi-Use version.
Step 7 – Kill the Colossus Boss
The vault door opens onto a corridor, and waiting at the bottom of the metal staircase inside is the Colossus — a Commander-class boss carrying a minigun loaded with depleted-uranium rounds. It patrols the ground level of the Armory inside a cloud of toxic green gas.
A few things to know before you push in:
- Explosives and grenades do no damage to the Colossus. Only direct gunfire works.
- Your team does not need to enter the gas cloud. Fight from the metal staircase and use the elevated angle as cover.
- The Colossus carries a $50,000 bounty tracked on the FOB Boss Board under the Commanders tab.
- It drops Military Composites when killed in the Armory — a valuable 3D printer ingredient. Check our full 3D printer recipes guide to see what you can craft with them.
Use a high-damage weapon with good sustained fire for this fight. The Kastov 762 loadout or the M4 loadout both work well here. For perk setup, see the MW4 perks tier list to maximize your survivability at Extreme threat.
Step 8 – Loot the Air Base Armory
With the Colossus down, you have full access to the Armory. The room contains:
- Ordnance crates — weapon and ammo supplies.
- Lockers and caches — random high-tier loot.
- The Armory Manifest — required to complete Operation Iron Citadel.
- The Air Base DRC Weapons Locker — opens only if you carry the Air Base DRC Weapons Locker Key (Ultra rarity). The locker moves around inside the room each deployment, so search the whole area.
After grabbing the Armory Manifest, plant explosives on the marked crates inside, then head out and plant more on the three strike aircraft — one in the hangar and two outside. Capture the SAM site and extract by chopper near the base fence to complete the mission.
The mission reward for completing Iron Citadel is the Supreme Leader’s Bunker Access Card. See our Supreme Leader’s Bunker Access Card guide for what to do with it next.
Air Base Armory Keys – What Each One Does
There are multiple keys tied to Chang-san Air Base. People often confuse them. Here is a quick breakdown:
- Air Base Access Card (Multi-Use) – Epic: Opens locked doors around the base during Iron Citadel. Used to enter Admin Complex No. 2 and upgraded into the Armory Keycard.
- Airbase Armory Keycard (Single Use) – Legendary: The upgraded version. Opens the Armory vault door together with the six-digit code. Made during Operation Iron Citadel — it is not a stash key.
- Air Base DRC Weapons Locker – Ultra: Opens only the DRC Weapons Locker inside the Armory. A separate key entirely. See our DRC Locker key guide for where to find it.
For a full breakdown of every key on the Hajin map, visit our complete MW4 DMZ keys and locations guide.
Tips Before You Run the Air Base Armory
- Always select Iron Citadel at deploy. It sets your spawn point close to the base and stops other squads from spawning in the same zone. It also gives you the objective markers that guide every step.
- Clear the guard tower first. It has line of sight on most of the base and will keep punishing you during the card search if you leave it up.
- Do not enter the Server Room without ammo. The alarm triggers the moment you upgrade the card. You need to fight your way to the bunker entrance immediately after.
- The code is different every time. Always collect all three notes. Never skip to the keypad without your full Known Digits on the HUD.
- Shoot the Colossus from the stairs. Staying elevated keeps you out of the gas and gives you a clean angle without needing to push into the cloud.
- Grab the DRC Locker key before you deploy if you have it in your stash. The locker is inside the Armory and this is your only window to use it.
Want to build a better setup before dropping into the air base? Check the best multiplayer loadouts for MW4, the best DMZ traits, and the full DMZ boss locations guide to prepare for everything Hajin throws at you.
You can also grab MW4 on Steam, PlayStation Store, or Xbox if you have not picked it up yet.
