ARC Raiders: How to Complete Magazine Geometry 101 by Damaging a Bastion with the Rattler

Magazine Geometry 101 is a research task in ARC Raiders that unlocks the Drum Mag amplification for the Rattler. It has two combat requirements wrapped into one job: pour 15,000 total damage into a Bastion using a Rattler, and destroy one Bastion with the same weapon. The research itself sits behind a level 4 Research Station and costs materials once you clear the field work.

Quick answer: Equip a Rattler, fight a Bastion from cover, and aim only at the yellow joints on its legs. Body shots often fail to register toward the 15,000 count, so stick to the weak points.

What the Magazine Geometry 101 task requires

The task has two steps you must finish during actual raids before you can research it at the station. Both have to be done with a Rattler specifically, so leave other weapons out of the equation for this one.

Use a Rattler to inflict 15,000 damage on a Bastion.
Destroy 1 Bastion with a Rattler.

Once both are complete, the research unlocks at a Research Station built to level 4, costing 5,000 Research Points and 5 Bastion Cell. Finishing it grants the Drum Mag upgrade, which feeds into the Amplified Rattler builds.

Why you aim at the yellow leg joints

A Bastion is heavily armored across its body, and shots into its center mass frequently fail to count toward the challenge total or give you XP. The yellow kneecaps on its leg joints are critical hit zones that reliably register damage, so every bullet you spend there moves the 15,000 counter forward.

Reward Passes menu showing a character from behind in a red flight suit with a backpack and a charm, beside a tier list. — The Reward Passes screen shows the Counter backpack charm, which needs another 7,650 to collect, with the Premium Pass upgrade offer at the lower right.

There is a second payoff to hitting the legs. Destroying a leg joint stuns the Bastion briefly, which opens a window to keep firing without taking return fire. The machine also has a yellow canister on its rear; breaking that peels back its rear plate and exposes a large weak part that takes major damage, which is useful when you reach the destroy-one step.

Watch the HUD counter climb as you land leg hits. If the number barely moves, you are hitting the body instead of the joints.

How to deal 15,000 Rattler damage safely

Equip the Rattler and carry plenty of Medium Ammo. It uses Medium Ammo and loads two rounds per reload, so dealing 15,000 damage will take a large supply. Ammo is inexpensive to craft or purchase, so stock up before dropping in.

Find a Bastion next to solid cover with an elevated vantage point. The catwalk above the Loading Bay Metro Station on Stella Montis works well, since a Bastion reliably spawns at the bottom of the loading bay there and the gantry gives you crates and barriers to duck behind.

Peek out from behind cover and fire the Rattler straight at the yellow leg joints. Hold your aim on those segments and let the counter tick up.

Targeting the Legs — Keep your fire on the yellow leg joints, not the armored body, so damage counts toward the task. Shown at 00:17 in Christian Konopatzki’s video. Image: Embark Studios

When your magazine runs dry, drop back behind a crate or wall to reload. The Rattler tops up two rounds at a time, so give yourself a safe moment rather than reloading in the open.

Using Cover and Ammo Tips — Reload behind solid cover; the Rattler refills two bullets at a time, so you need a quiet moment. Shown at 00:32 in Christian Konopatzki’s video. Image: Embark Studios

Lean back out and resume firing on the legs. The Bastion screeches before unloading its gatling gun at your last known position for about three seconds, so duck back whenever it winds up and wait out the volley.

Peeking and Sustained Fire — Peek, fire a burst into the joints, then drop back when the Bastion winds up its gatling gun. Shown at 00:38 in Christian Konopatzki’s video. Image: Embark Studios

Repeat the peek-fire-reload loop until the counter reaches 15,000. Because a single Bastion has only 2,050 body health, you will likely cycle through several machines across runs to reach the full damage total, so stay patient and keep returning to the loading bay.

Body Hits vs Leg Hits — A smoking Bastion in the loading bay; keep hitting joints rather than the smoking hull to make progress count. Shown at 00:54 in Christian Konopatzki’s video. Image: Embark Studios

The 15,000 figure is cumulative across the whole task, not per Bastion. You do not need to hit it in one fight, so you can chip away over multiple raids and still bank progress.

Bastion weak points and health values

Knowing exactly how much each Bastion part can take tells you where your Rattler rounds do the most work. The leg joints and the rear core are the parts that matter here.

Bastion part	Health
Body	2,050
Core	5,000
Upper leg	280
Lower leg	180
Joint	180
Medium armor plate	48

The Bastion itself deals 6.5 damage from its turret and 0.5 from a body attack, which is why moving behind cover during its gatling volley keeps you alive. When you salvage a destroyed one, you pull a Bastion Cell, the exact material the research consumes, so every Bastion you kill for the destroy step also stocks the research cost.

Bastions patrol wide open areas on every map. Beyond the Stella Montis loading bay, dependable spawns sit under the Cielo Sereno Observatory on Pendola Pass and around Market Ruins, Marano Park and north of Plaza Rosa on Buried City.

Topographic Destinations map with labeled locations and rounds played counters such as 6/25 for Pendola Pass. — The Destinations map lists Pendola Pass, Spaceport, Stella Montis, The Blue Gate, Riven Tides, Buried City, Dam Battlegrounds, ARC Frigate and the Practice Range, with rounds played shown on the locked ones.

Rattler stats you are working with

The Rattler is a common, fully automatic assault rifle. Its small magazine and two-at-a-time reload are the limiting factor during this task, which is why ammo stock and cover timing matter so much.

Attribute	Value
Category	Assault Rifle
Ammo	Medium Ammo
Firing mode	Fully-Automatic
Magazine size	12 (I), 16 (II), 20 (III), 24 (IV)
ARC armor penetration	Moderate
Mod slots	3
Rarity	Common

Higher weapon levels raise the magazine size, so a Level IV Rattler holds 24 rounds and cuts down how often you have to duck back and reload during the fight. The gun can be amplified with Drum Mag, Incendiary Rounds and More Reload once the research is done.

How to confirm the task is complete

The HUD tracker in the top-left shows your running total against 15,000 while you fight, so you can watch it approach the goal in real time. Once both the damage and the destroy-one steps clear, the research becomes available at your level 4 Research Station. Spend the 5,000 Research Points and 5 Bastion Cell there to finish Magazine Geometry 101 and add the Drum Mag upgrade to your Rattler amplification options.

Quest complete panel with 1,000 XP, a rifle and an ammo pack of 80 as rewards, beside a headphoned guard at monitors. — The PICKING UP THE PIECES quest is shown as COMPLETE with 1,000 XP, a tier III rifle and an ammo stack of 80 as rewards, and Shani’s closing line below.