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Armored Core 6 S-Rank Guide (Chapter 4)

Find the S-ranks the PCA are desperately trying to protect.

For those that have made it this far, prepare yourself. Some of Armored Core 6’s most infamous battles lie in Chapter 4. Your builds and your piloting skills will both need to be at their best to secure S-ranks in these missions.

S-rank guides for other chapters can be found here:

Underground Exploration – Depth 1

Chapter 4’s S-ranks start with a breather. This mission is comedically easy due to the Pulse Scutum existing. Bring a heavyweight with this shield and an extra gun to take out a few mechs with. Once you’re in the mission, just hold your shield out, aim down and fall towards the Nephentes. You’ll fall faster if you don’t move horizontally. If you line up near one of the elevator platforms on the side, many of its attacks will be blocked by the infrastructure. Anything that gets past will have its damage massively reduced by your shield.

Underground Exploration – Depth 2

This mission leaves a lot of room for ammo and repair costs in its S-rank. It mainly just wants you to finish quickly. Most of the level is spent navigating corridors with few required fights. Without objective markers, you’ll need to memorize the layout and move quickly.

Start by heading down the corridors until you reach a locked door. The controls are found in the room to the left, down a shaft. Activating them will open an elevator next to you that you can ride back to the locked door.

G5 Iguazu will be waiting for you down the next hallway. He packs an array of missiles and rifles to pressure you, as well as a shield to protect himself. It’s easy to back him into a wall or corner, where it becomes much easier to stagger him. Keep the pressure on him and he’ll quickly crack.

Enforcer Boss

The Enforcer boss doing a ground shockwave attack
From Software / Dominic Allain

After Iguazu’s arena, you’ll find yourself in a chasm being sniped by the Enforcer. You can’t defeat it yet, so fly towards the end of the chasm to find a vent lower down. Head inside, travel through some more corridors, and hack the control panel at the end. There’s some PCA mechs that will ambush you, so deal with them before continuing. An elevator nearby will open up and take you to the level’s boss.

The Enforcer is very mobile and uses mostly energy weapons. You’ll need to use vertical movement to avoid its attacks. For the first phase, staying airborne protects you from its melee attacks. This leaves its highly accurate lasers as the main threat. In phase two, it gains new melee attacks that it can perform midair. Watch for when it charges up, then quick boost to dodge. Otherwise, treat this like any other AC fight. Focus on staggering it quickly and dealing massive damage once you’ve done so.

Underground Exploration – Depth 3

Depth 3 is much easier to deal with than Depth 2. Head straight for the reactor where your next objective lies. There will be some lasers sniping you along the way but staying at low altitude will prevent them from shooting you. The door to the reactor is around the back of the structure. It’s a fairly linear path to the core, but you’ll have to fight some PCA mechs along the way.

Once the core is destroyed, head back to the entrance to find the Ephemera waiting to ambush you midway. It has some strong energy attacks, including the Moonlight sword, but it’s otherwise the same as any other AC. Destroy it and exit the reactor to finish the mission.

Intercept the Redguns

For an aspiring S-ranker, this mission is quite the problem child. Your build must balance heavy firepower with efficient crowd control, while still being able to mitigate all the damage that will be thrown back at it. For that reason, I’m actually going to recommend something specific.

Build Recommendation

An example build for S-ranking "Intercept the Redguns"
From Software / Dominic Allain

I’ve found good success with this build. The laser rifle and generator combo destroy most cannon fodder with one shot, and the Earshots will handle anything bigger. As with anything in Armored Core, you can tweak things to fit your playstyle. The important concepts here are the ability to stay airborne for extended periods and mid-range weapons to complement it. Ransetsu-RFs or Ducketts with melee are good alternatives.

From the start, you’re thrown into a pit of Balam MTs. Reinforcements arrive as part of five distinct waves, each on a timer. The first three waves are simple to deal with, mainly consisting of weak MTs. They aren’t very bulky but are armed with missiles and grenade launchers. Stay airborne to avoid splash damage from them. A tetrapod MT will arrive as part of the third wave, so make destroying that a priority.

Michigan’s Arrival

G1 Michigan deploying into "Intercept the Redguns"
From Software / Dominic Allain

G1 Michigan will arrive as part of the fourth wave. Hope you’ve destroyed the tetrapod by then. Aside from some spread missiles, his entire kit falters outside of close-range. Use your aerial mobility to keep distance from his gatling gun and Songbirds. Pulse Armor will let you match Michigan’s aggression for a time if you have any close-range weapons. If he Assault Boosts towards you, he’s going to use his explosive thrower melee. Get in his face and circle behind him to dodge it.

It’s very likely that the fifth wave will arrive before you’ve finished dealing with Michigan and his MT squad. Even worse, another tetrapod MT shows up in it. Circle around the wreckage and avoid taking on both at once. After you defeat Michigan, it’s just cleanup duty from here.

Ambush the Vespers

Compared to the last mission, this one may as well be free. You’ll be assisting Middle Flatwell to take out two ACs, Pater and Hawkins. Despite the mission calling for an ambush, you can and should walk right up to the door they’ll appear out of. When it opens, give them a deadly surprise. As a bonus, this will likely push them back into the room they came from. It’s an extremely tight space, which is a serious boon for any close-range build. Treat this like you would any other AC battle and you’ll come out with an easy S-rank.

Unknown Territory Survey

This mission has some more exploration fluff, but you can just boost past it. It’s a long setup for the real meat of the mission: a one-on-one AC duel. You’re up against Rusty this time around. His AC is agile and tries to keep constant pressure on you. If you get staggered, he’s got a powerful laser slicer to combo with. Rusty may be a tough opponent, but it’s nothing your usual dueling build can’t handle.

Reach the Coral Convergence

For this mission, bring something that can stagger enemies as quickly as possible and at least one melee weapon to punish. Your first objective is to take out a squad of MTs and two ACs. As you arrive on the scene, both ACs will be close to staggering. Take advantage of this and wipe one out immediately. Focus on the other AC next, then the MTs.

After they’ve been dealt with, keep following the objective markers through the rest of the level. Ignore any enemies along the way. Before you jump into the boss arena at the end, take the resupply point. You’ve gotta be in top form for what’s coming.

Cel-240 Boss

Ibis Series Cel 240 in phase 2 of its fight
From Software / Dominic Allain

Ibis Cel-240 is waiting for you at the bottom. Stay mobile and keep dodging its lasers until it goes for a melee attack. If you have missiles, use them to chip away and maintain its stagger bar. Once it performs a melee attack, Ibis leaves a relatively big opening. Now is the perfect time to hit it with big attacks of your own. Keep this momentum and play aggressively to finish phase 1.

The second phase plays similarly to the first. Remain on the ground and always keep moving. Don’t bother attacking it until the health bar reappears at the top, as Ibis is immune to damage until then. When it uses another melee attack, repeat the phase one strategy. Exploit the opening and deal as much damage as you can in a single stagger.


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