The fourth season of Call of Duty: Modern Warfare 3 is in full swing, and as of 2026, the initial set of Weekly Challenges has been deployed. For the entire duration of the season, a fresh batch of objectives will be released weekly, but players have the flexibility to complete them at any point before the season concludes. These tasks are segmented across the game's three primary modes: Multiplayer, the cooperative Zombies experience, and the expansive battle royale of Warzone. The incentive is compelling: complete any five challenges from the current week's list, and you'll secure an exclusive reward, which can range from a powerful new aftermarket attachment to a unique weapon or a coveted cosmetic item. This week, the prize is the formidable JAK Harbinger Kit, a conversion kit designed for the iconic M4 assault rifle. This attachment fundamentally alters the weapon's role, morphing it into a devastating .50 Caliber battle rifle. Players are encouraged to dive into their preferred playlists, equip a recommended firearm, and start tackling challenges to earn some of Modern Warfare 3's most distinctive gear.

Week 1 Challenge Reward: The JAK Harbinger Kit

Securing any five of this week's varied challenges will grant you the JAK Harbinger Kit for the M4. This isn't just a simple attachment; it's a complete overhaul. The kit transforms the M4 into a high-caliber battle rifle, dramatically boosting its damage output per shot. This power comes with trade-offs, notably a reduced rate of fire and increased recoil. However, the developers have thoughtfully adjusted the weapon's visual feedback—like gun smoke and perceived kick—to meet Modern Warfare 3's modern standards, making the kit more manageable than its raw stats might suggest once a player acclimates to its rhythm.

From a statistical perspective, this conversion kit objectively surpasses weapons like the Sidewinder in its damage class. It delivers a staggering 101 damage per shot with a fire rate of 245 RPM, enabling it to eliminate opponents with just two well-placed shots. Be prepared for adjustments, though, as the kit also imposes penalties on handling and mobility stats, encouraging a more deliberate, tactical playstyle.

Multiplayer Challenges Breakdown

For those who thrive in traditional player-versus-player combat, the Multiplayer challenges offer a mix of skill-based and grind-oriented objectives. Remember, "recommended" weapons are easily identified by a small flame symbol next to their icon in the Create-A-Class menu.

Zombies (MWZ) Challenges Breakdown

Venturing into the undead-infested zones of MWZ presents a different set of trials. These challenges often require slaughtering hordes of zombies under specific conditions, making them ideal for cooperative play.

• Get 300 kills while ADS with a recommended assault rifle. (2,500 XP) – A straightforward task for holding a position.

• Get 150 kills with a recommended weapon after having recently swapped weapons. (5,000 XP) – You must secure the kill roughly two seconds after switching weapons for it to count.

• Get 3 Disciple kills with a recommended weapon. (5,000 XP) – Target the specific, vampiric Disciple enemy type.

• Get 100 hipfire kills with a recommended SMG. (5,000 XP) – Get up close and personal without aiming down sights.

• Get 200 kills with Cryofreeze ammo installed on a recommended assault rifle. (7,500 XP) – Cryofreeze ammo can be found in Strongholds, as Contract rewards, or crafted if you have the schematic.

• Get 300 kills with a Pack-A-Punched recommended weapon. (7,500 XP) – Investing in a Pack-A-Punch machine is essential for this one.

• Get 100 kills with a melee weapon. (10,000 XP) – A classic and chaotic Zombies challenge.

Warzone Challenges Breakdown

For the battle royale specialists, the Warzone challenges for Season 4 focus on exploration, contract completion, and demonstrating prowess in specific regions of the massive Urzikstan map.

Here are the key objectives:

1. In Warzone, open 75 loot caches. (2,500 XP) – A simple but time-consuming looting task.

2. In Urzikstan, kill 15 operators in the northwest region (Resort, Power, Seaport, Cargo). (5,000 XP) – Hot-drop into these popular areas.

3. In Urzikstan, kill 15 operators in the southern region (City, Suburbs, Manor). (5,000 XP) – Shift your focus to the southern urban sprawl.

4. Complete 15 Contracts. (5,000 XP) – A great way to earn cash and challenge progress simultaneously.

5. In Urzikstan, kill 15 operators in the eastern region (Military Base or Farms). (7,500 XP) – The Military Base is often a high-traffic combat zone.

6. In Urzikstan, kill 15 operators in the central region (Old Town, Low Town). (7,500 XP) – Navigate the tight corridors of these central locales.

7. In Warzone, place in the top ten 7 times. (10,000 XP) – Prioritize survival and strategic positioning to consistently finish high.

Final Strategy Tips

To efficiently unlock the JAK Harbinger Kit, players should adopt a hybrid approach. Focus on completing the easiest or most natural challenges from each mode that align with your playstyle. For instance, a Multiplayer enthusiast might combine the "finish matches with a party" challenge with a few weapon-specific kills. A Zombies player can easily rack up the Pack-A-Punch and hipfire SMG kills in a single successful session. Warzone players can work on region-specific kills while also completing contracts and looting. By mixing and matching objectives across modes, you can reach the five-challenge threshold faster and add a powerful new tool to your Modern Warfare 3 arsenal. Remember, these challenges remain active all season, so there's no need to rush—play smart and claim your reward.