Arc Raiders: How to Unlock the Drum Mag for the Amplified Rattler

The Drum Mag turns the Rattler into a 64-round sustained-fire gun, but it sits deep in the weapon’s amplification tree and only opens once your workshop is maxed out. It is not a loot drop or a craftable attachment. You unlock it by taking the weapon to its final tier, amplifying it, and clearing a research project that asks you to fight Bastions.

Quick answer: Upgrade a Rattler to tier IV, amplify it with an Amplification Module Mk. I at Gunsmith IV, take the More Reload node, then complete the Magazine Geometry 101 research at Research Station level 4 to unlock and buy the Drum Mag.

What the Drum Mag does to the Rattler

The Drum Mag increases the magazine by +40 rounds. For an amplified Rattler, capacity rises from 24 at tier IV to 64. The weapon feeds ammunition in small batches instead of replacing the whole magazine, so the larger reserve helps you keep fighting but doesn’t make reloads quicker.

Gun Shop trade menu with a tooltip for Medium Ammo listing compatible weapons, beside a purchase panel set to ×20. — Medium Ammo is highlighted in the Tian Wen Gun Shop, with a tooltip listing Rattler, Tempest, Arpeggio, Renegade and Torrente as compatible weapons.

That capacity comes with handling penalties. Expect noticeably more recoil and wider spread, so pair the build with recoil-control mods if you plan to fire long bursts at range.

+40 magazine size (64 rounds total)
+50% vertical recoil
+50% horizontal recoil
+30% max shot dispersion and +30% base dispersion
+10% ADS dispersion and -10% ADS speed

What you need before you start

Amplification is an endgame system, so several pieces of progression have to be in place first. Line these up before you touch the Rattler, or the Drum Mag node will stay locked.

A Rattler upgraded all the way to tier IV.
Gunsmith at level IV, which requires the Outpost expanded to level 4.
Research Station at level 4 for the Amplified Research tab.
One Amplification Module Mk. I, scavenged from ARC Topside.
Materials for the tree nodes: Propellant Valve Assembly and Pressure Regulator.

The Amplification Module Mk. I is required for all common weapons, including the Rattler. This advanced ARC component comes from high-value ARC targets, not vendors, so collect one during a raid before committing to the build.

Quest log with Picking Up the Pieces objectives, a Rattler III assault rifle tooltip, and rewards, beside a seated operator at monitors. — Shani’s QUESTS screen shows the PICKING UP THE PIECES quest with a RATTLER III Assault Rifle (Common) tooltip over the 1,000 XP rewards.

Upgrade the Rattler to tier IV

At tier IV, the weapon’s durability limit is 130; Amplification raises it to 200. Upgrade the gun to its highest tier before applying Amplification. Advance through the regular tiers at the Gunsmith.

Open your inventory stash and select a Rattler, then choose Upgrade. Spend Metal Parts and Rubber Parts to take it to Rattler II, which adds durability and magazine size.

Opening Inventory & Upgrading Rattler I — The Rattler I upgrade screen, where you spend parts to begin climbing the tiers. Shown at 00:21 in Quick Tips’s video. Image: Embark Studios

Upgrade to Rattler III using Mechanical Components and Simple Gun Parts. This raises the base magazine to 20 rounds.

Push the weapon to Rattler IV with another set of Mechanical Components and Simple Gun Parts. The tier IV magazine holds 24 rounds, and the gun is now ready to amplify.

Amplify the Rattler and take the More Reload node

Use the Gunsmith’s Weapon Upgrades tab to apply Amplification. Perk selections are then locked to that individual weapon, so plan your choices on the way to the Drum Mag.

Select the Rattler IV in the Weapon Upgrades tab and press Amplify. It consumes one Amplification Module Mk. I, raises max durability to 200, and repairs the gun. This unlocks the Amplified Durability node that the rest of the tree branches from.

Inspecting Drum Mag & Amplification Requirements — The amplification requirements on the Rattler IV: an Amplification Module Mk. I and Gunsmith level IV. Shown at 00:48 in Quick Tips’s video. Image: Embark Studios

Buy the More Reload node first. It increases how many bullets load at once (+2) and is the prerequisite that leads directly into the Drum Mag. This node costs 2 Propellant Valve Assembly.

The Drum Mag cannot be purchased until More Reload is already applied. The Incendiary Rounds node branches off separately, so it is not required for the Drum Mag path.

Complete the Magazine Geometry 101 research

The Drum Mag node stays locked until you finish the two-step Magazine Geometry 101 project in the Amplified Research tab. This needs the Research Station at level 4.

To complete this step, use a Rattler to inflict 15,000 damage on a Bastion, then destroy 1 Bastion with a Rattler. The Rattler must be used for both objectives.

Turn in the second step’s cost of 5,000 Research Points and 5 Bastion Cells. Bastion Cells drop from Bastions, so you can bank them during the step one fights.

With the research done, open the Rattler’s tree and buy the Drum Mag node. It costs 4 Pressure Regulator on top of the completed research. The upgrade is then permanently part of that weapon.

Rattler reference stats

Use these base figures to plan the climb to tier IV and to judge what the Drum Mag changes. The Rattler is a common assault rifle that fires fully automatic Medium Ammo with moderate ARC armor penetration, weighs 6, and carries three mod slots.

Tier	Magazine size	Notes
Rattler I	12	Base tier
Rattler II	16	+4 magazine, +10 durability
Rattler III	20	Durability 120
Rattler IV	24	Durability 130, ready to amplify
Amplified + Drum Mag	64	Max durability 200

The amplified Rattler weighs 6 and sells for 11,200. If you ever retire it, recycling returns 16 Amplified Fragments and salvaging returns 10, while repairs cost 27 Amplified Fragments for half its durability.

How to confirm the Drum Mag is applied

Open the amplified Rattler in your inventory and check its stats. A magazine size of 64 confirms the Drum Mag is active, and the weapon’s name updates to the amplified variant with the More Reload and Drum Mag perks listed on its tree.

Reviewing Amplified Rattler Stats with Drum Mag — The finished amplified Rattler reads a magazine size of 64, the clearest sign the Drum Mag is equipped. Shown at 01:22 in Quick Tips’s video. Image: Embark Studios

From here you can still add Incendiary Rounds on top of the More Reload and Drum Mag combination if you want burn damage as well, though that is a separate research and material cost. For most players, the 64-round magazine alone is what makes the amplified Rattler worth the trip through the full tree.