Hanwha Defense USA partners with U.S. Army on 58-caliber cannon for K9 next-generation howitzer.

Hanwha Defense USA has signed a CRADA (Cooperative Research and Development Agreement) with the U.S. Army Combat Capabilities Development Command Armaments Center to integrate a government-designed 58 caliber 155mm cannon onto the K9 self-propelled howitzer. The effort reflects the U.S. Army’s urgency to regain long-range fires dominance as the 39-caliber M109A7 Paladin approaches the limit of its growth potential.

Hanwha Defense USA disclosed in December 2025 that it has entered into a Cooperative Research and Development Agreement with the U.S. Army’s DEVCOM Armaments Center to evaluate the integration of a 58 caliber 155mm cannon on the K9 155mm self-propelled howitzer platform. According to company statements and U.S. Army development goals, the collaboration aims to accelerate extended-range artillery concepts by leveraging an already fielded, combat-proven chassis, rather than waiting for a clean-sheet replacement for the Paladin fleet.
Follow Army Recognition on Google News at this link

A K9 Thunder 155mm self-propelled howitzer advances across the training area during a combined live-fire exercise conducted as part of Exercise Talisman Sabre 25. (Picture source: U.S. Department of War)

The K9 Thunder, developed by South Korea and in widespread service with multiple NATO nations, is a 155mm tracked self-propelled howitzer originally equipped with a 52-caliber barrel. The K9’s baseline configuration has already demonstrated significant improvements in range and firepower over legacy U.S. systems. Standard K9 units can achieve ranges up to 40 kilometers using rocket-assisted projectiles and up to 54 kilometers with advanced extended-range munitions. However, with adversary systems now routinely firing beyond 60 kilometers, the U.S. Army has prioritized the development and integration of longer barrels, more advanced propellants, and next-generation projectiles.

The 58-caliber cannon under development in the United States was initially tested as part of the Extended Range Cannon Artillery (ERCA) program, a pillar of the Army’s Long-Range Precision Fires (LRPF) modernization strategy. A 58-caliber designation indicates that the barrel length is 58 times the internal diameter of the cannon, in this case 155mm, allowing for a longer internal pressure zone, increased muzzle velocity, and substantially extended projectile range. Compared to the 39-caliber M284 cannon currently mounted on the M109A7, the 58-caliber system enables the same shell to travel nearly twice as far, with engagement distances exceeding 70 kilometers under operational conditions.

This increase in barrel length also brings technical advantages beyond pure range. Higher muzzle velocity improves projectile stability, reduces time of flight, and enhances accuracy against time-sensitive targets. It also enables effective employment of future precision-guided and hypersonic-assisted artillery munitions designed to operate at greater standoff distances. The tradeoff is significantly higher recoil forces and thermal stress, which require a robust chassis, reinforced turret structure, and sufficient onboard power and cooling capacity.

In this context, the K9 howitzer offers a decisive advantage. Designed from the outset to accommodate a 52-caliber gun, the K9 already incorporates structural margins that allow it to grow to a 58-caliber configuration without compromising mobility or survivability. The system features a fully armored turret, advanced digital fire control, automated ammunition handling, and rapid shoot-and-scoot capability, all of which are essential in high-threat counter-battery environments.

While Hanwha’s CRADA with DEVCOM-AC marks the first formal U.S. military integration effort between the 58-caliber cannon and the K9 platform, it is not the only approach being explored by the Army. At the AUSA 2025 Annual Meeting in Washington, D.C., BAE Systems displayed a new M109 concept variant fitted with a Rheinmetall 58-caliber 155mm gun. That demonstrator highlighted the Army’s broader interest in extending the life and relevance of existing platforms through hybrid solutions, but it remains at a conceptual and evaluation stage without a defined production timeline.

By contrast, the K9 is a mature, combat-proven system with more than 1,700 units delivered or on order worldwide and active production lines in several allied countries. Six NATO members currently operate the K9, including Poland, Norway, Finland, and Estonia. Notably, four of the five NATO countries that share a land border with Russia rely on the K9 as their primary long-range artillery system. This widespread adoption has created an established multinational sustainment and logistics ecosystem that would directly benefit U.S. forces operating alongside allies in Europe.

From an industrial perspective, Hanwha Defense USA has steadily expanded its footprint within the United States, investing in local supply chains, workforce development, and manufacturing partnerships. This approach aligns with Pentagon priorities to strengthen the domestic defense industrial base and to leverage proven allied designs to accelerate capability delivery.

The CRADA framework allows the U.S. Army to evaluate technical integration, recoil management, ammunition compatibility, and system durability without committing to immediate procurement. Army Recognition understands that this effort is expected to lead to live-fire testing and detailed performance assessments in 2026, which will inform the U.S. Army’s Tactical Fires Modernization roadmap.

As the U.S. Army moves toward a new generation of self-propelled howitzers capable of dominating extended-range engagements, the combination of a U.S.-developed 58-caliber cannon with the battle-proven K9 platform represents a pragmatic and strategically aligned solution. Rather than waiting for a clean-sheet design to mature, the Army is increasingly looking to field-ready systems that can deliver decisive effects now, while remaining adaptable for future technological evolution.

In this context, the South Korean K9 155mm self-propelled howitzer stands out as more than merely a foreign-candidate platform. It represents a realistic pathway for rapidly restoring U.S. artillery dominance across multiple theaters, supported by allied interoperability, industrial scalability, and a clear growth margin for the next generation of long-range precision fires.

Written by Alain Servaes – Chief Editor, Army Recognition Group
Alain Servaes is a former infantry non-commissioned officer and the founder of Army Recognition. With over 20 years in defense journalism, he provides expert analysis on military equipment, NATO operations, and the global defense industry.