ARC Raiders: How to Unlock Incendiary Grenades on the Hullcracker and Rascal

Flame rounds on the Hullcracker and Rascal come from a single amplification upgrade called Incendiary Grenades. It sits at the far end of each weapon’s progression, so you cannot simply buy it or bolt it on. You have to fully upgrade the launcher, amplify it with ARC technology, and then pay a rare material cost to light the node up.

Quick answer: Upgrade the weapon to tier IV, amplify it with an Amplification Module looted from the ARC Frigate, then unlock the Incendiary Grenades node using 3× Fossilized Lightning after researching Compact Combustion Charges.

What Incendiary Grenades do on the Hullcracker and Rascal

Both weapons are anti-ARC grenade launchers whose explosive rounds only detonate when they strike ARC machines. The Incendiary Grenades upgrade adds an incendiary compound to the projectile so that, on detonation, it spreads fire across the target and burns it over time.

That damage over time comes with trade-offs. On the Hullcracker the upgrade applies these exact changes:

Trader menu with Launcher Ammo tooltip, limited stock panel, 4,500 coin price and a disabled purchase button locked until level 12. — In Tian Wen’s GUN SHOP, the Launcher Ammo trade is a rare limited-stock item priced at 4,500 coins that unlocks at level 12.

+11.25/s Burn Damage
+5s Burn Duration
40% reduced projectile damage
50% reduced projectile velocity

You trade a chunk of direct impact and a slower, more arced shot for a lingering burn. Because the round only arms against ARC, none of this works on other players, so treat it purely as a boss-and-heavy tool.

What you need before you start

Incendiary Grenades is an amplification upgrade, which means the whole chain of requirements has to be in place first. Gather these before you commit any materials:

A tier IV weapon (Hullcracker IV or Rascal IV)
An Amplification Module matching the weapon’s rarity
The Compact Combustion Charges research completed
3× Fossilized Lightning, an Epic material found in the wild

Fossilized Lightning is an Epic material sourced from nature, and the upgrade consumes three of it. Stockpile all three before you open the node so you are not forced to leave a raid mid-build.

Reward Passes screen showing a large weathered assault rifle over a dark circle with a golden glow, level track on the left. — The Reward Passes screen previews the Bettina II, an Epic Assault Rifle at level 41, with 6,150 more to earn before it can be collected.

Unlock Incendiary Grenades on the Hullcracker

Open the weapon upgrade menu from your Stash or Loadout and select the Hullcracker. Work it up the standard crafting path to tier IV using the usual parts, such as Advanced Mechanical Components and Heavy Gun Parts. Amplification only appears once the weapon reaches Hullcracker IV.

Inspecting Weapons and Upgrades — The Hullcracker upgrade screen, where you push the launcher up to tier IV before amplification becomes available. Shown at 00:34 in Quick Tips’s video. Image: Embark Studios

Get an Amplification Module. The Hullcracker is an Epic weapon, so it needs an Amplification Module MK. IV to amplify. Modules are looted from containers on and around the ARC Frigate, the hostile craft that hovers over areas like Dam Battlegrounds. Head to the active Frigate destination and search its exterior.

Amplification Module Requirement — Your stash with the Amplification Module and component parts you need in hand before amplifying. Shown at 00:57 in Quick Tips’s video. Image: Embark Studios

Apply the module to Hullcracker IV. This converts it into the Amplified Hullcracker and grants Amplified Durability automatically, then opens the amplified branch where Incendiary Grenades and Mag Reload live.

Select the Incendiary Grenades node. Spend 3× Fossilized Lightning to unlock it. If the node is greyed out, you still need the Compact Combustion Charges research done first. Once it resolves, every round that detonates on ARC spreads fire and applies the burn.

Incendiary Grenades Upgrade Details — The Incendiary Grenades node, listing its burn effect and the Fossilized Lightning cost you pay to activate it. Shown at 01:27 in Quick Tips’s video. Image: Embark Studios

Unlock Incendiary Grenades on the Rascal

The Rascal follows the same path with two differences. It is a Rare weapon, so amplification takes an Amplification Module MK. III rather than the Hullcracker’s MK. IV. Take it to Rascal IV, apply the module to create the Amplified Rascal, and the amplified branch opens up.

The Rascal’s amplified branch holds three perks: High Velocity, Sprint Shooting, and Incendiary Grenades. Only the fire upgrade matters here. It needs the Compact Combustion Charges research and the same 3× Fossilized Lightning. Pick that node, pay the cost, and the Rascal’s explosive rounds spread fire on ARC exactly as the Hullcracker’s do.

Hullcracker and Rascal amplification reference

Both launchers share the Special category and the Launcher Ammo feed, but they sit in different weight and rarity classes, which is what sets their module requirement. Use this to plan which weapon to amplify first.

Weapon	Rarity	Weight	Module to amplify
Hullcracker	Epic	7	MK. IV
Rascal	Rare	4	MK. III

The Incendiary Grenades node carries an identical cost on both weapons, so the material farm is the same no matter which one you build:

Node	Research	Material cost
Incendiary Grenades (Hullcracker)	Compact Combustion Charges	3× Fossilized Lightning
Incendiary Grenades (Rascal)	Compact Combustion Charges	3× Fossilized Lightning

Amplification Modules themselves scale by rarity: MK. I unlocks common amplification, MK. III unlocks rare, and MK. V unlocks legendary. That is why the Rare Rascal and the Epic Hullcracker ask for different module tiers.

How to confirm the flame rounds are active

After you pay the Fossilized Lightning cost, the weapon’s name updates to reflect the upgrade, for example Amplified Hullcracker (Incendiary Grenades). The Incendiary Grenades node in the amplified tree shows as unlocked rather than locked, and the weapon’s stat card lists the burn damage and burn duration alongside the reduced projectile damage and velocity.

Reward passes menu displaying a large heavy launcher-style weapon named Hullcracker IV in a dark circle. — The REWARD PASSES screen shows the HULLCRACKER IV special epic weapon at level 34, needing 5,100 more to collect.

In a raid, the clear confirmation is the effect itself. Land a round on an ARC machine and it will catch fire, taking continued burn damage after the initial detonation. Once you see that lingering burn, the upgrade is working as intended.