• Military Menu                       

• Introduction
• Systems
• Facilities
• Agencies
• Industry
• Operations
• Countries
• Hot Documents
• News
• Reports
• Policy
• Budget
• Congress
• Links

• WMD
• Intelligence
• Homeland Security
• Space

The Type 63 120-mm mortar is the Republic of China's domestically produced copy of the Israeli Soltam K5 120-mm mortar, developed through reverse engineering rather than licensed production. The system underwent a number of design improvements and currently serves with battalion-level units of the Republic of China Army and Marine Corps as their principal heavy mortar fire support weapon. Produced by Joint Logistics Factory 202 (formerly Arsenal 61 under the Armaments Bureau), the Type 63 represents both Taiwan's capability for indigenous weapons production and the limitations inherent in copying foreign designs without access to complete technical documentation and supporting systems integration.

These 120-mm mortars were designed to provide infantry with a mortar capable of very effective 120-mm ammunition fire but sufficiently light to enable it to be moved by jeep-type vehicles, transported by a mule, carried by a detachment of three soldiers, moved in a helicopter, or dropped by parachute. The design philosophy emphasized mobility and tactical flexibility, allowing the weapon to support rapidly maneuvering infantry formations across varied terrain. The system fills the role of battalion-level heavy fire support, providing indirect fire capabilities substantially more powerful than company-level light mortars while remaining more mobile and responsive than towed artillery.

Technical Specifications

Technical Description

The barrel is constructed from high-quality alloy steel tube with a honed interior, providing the necessary strength to withstand repeated high-pressure firings while maintaining accuracy over the weapon's service life. The lower end is externally screw-threaded to accept the breech piece, which holds the fixed firing pin. To ensure safety while dealing with a misfire, there is a safety catch which, when rotated, draws the pin back into the interior of the breech piece, preventing accidental detonation during malfunction clearance procedures. The lower end of the breech piece is shaped into a ball which enters a socket in the baseplate, providing the articulation necessary for elevation and traverse adjustments. The most obvious difference from the original Israeli version is that the Type 63 draws on American mortar design concepts, incorporating cooling grooves from the rear third of the barrel to the bottom that reduce weight, strengthen the structure, and improve heat dissipation efficiency during sustained firing.

The bipod legs have spikes at the bottom for ground anchoring and are joined at the elevation gear housing. The distance between the legs is controlled by an adjustable length of chain, allowing the crew to configure the weapon's footprint based on terrain and tactical requirements. The lower end of the elevation column, which contains the elevation screw thread, is attached to the left leg of the bipod by a cylinder containing a screw thread. The rotation of the handle at the end of this thread moves the elevation column out of the vertical and permits the mortar to be cross-leveled to compensate for irregularities in the ground, ensuring accurate fire even when emplaced on uneven terrain. At the top end of the elevating column is the yoke, which holds the sight at the left and the traversing handle at the right. The thread of the traversing gear, like all the threads in this mortar, is completely enclosed to protect against dirt, moisture, and combat damage.

Development History and Procurement

In 1975 (Republic of China year 64), the Republic of China's Joint Logistics Factory 61 (Arsenal Department of Armaments Bureau 202) was originally ordered to negotiate with Israel's Soltam Military Industry Ltd. for the purchase of K-5 mortar related technology and authorized production rights. However, the Israeli company quoted a license fee exceeding 3.6 million U.S. dollars, plus additional royalties to be paid during production for each unit manufactured. Factory 61 management determined this price was excessive and made the decision to reverse-engineer the weapon through technical intelligence gathering rather than pursue legitimate technology transfer.

The opportunity for reverse engineering presented itself through Taiwan's military cooperation with Singapore. The Singapore Armed Forces, which conducted training in Taiwan under the codenamed Starlight Force program, employed the Soltam K-5 mortar in their inventory and requested that Joint Logistics Factory 61 provide maintenance support for these weapons during Singapore's training rotations on the island. Factory 61 personnel took advantage of this maintenance assistance arrangement to conduct detailed design surveys and complete comprehensive technical drawings of the K-5 system. This process allowed Taiwanese engineers to document critical dimensions, material specifications, and assembly procedures without formal access to Israeli technical data packages or manufacturing documentation.

The design was finalized in March 1975, and a reverse-engineered prototype was completed in April 1975, demonstrating remarkably rapid development from initial surveying to functional hardware. The test firing results proved satisfactory, validating the basic soundness of the copied design. Factory 61 continued to modify the artillery design independently before formal finalization, incorporating improvements based on available manufacturing technology and materials. The Type 63 was quickly finalized, entered mass production to meet Republic of China Army requirements, and was even sold in small quantities to the international arms market, generating modest export revenue.

Design Evolution and Technical Heritage

The design prototype of the K-5 traces back to the 120 KRH/40 mortar manufactured by Finland in the late 1930s, which was itself based on the Soviet PM1938 mortar. By the time Taiwan undertook its reverse engineering project, the relevant technology was mature and well-understood internationally. However, Factory 61 engineers used manufacturing technology of the 1970s to optimize the design, employing contemporary steels and making adjustments to heat treatment processes and basic design parameters. These modifications, particularly the incorporation of heat dissipation grooves inspired by American mortar designs, reduced the total weight of the Type 63 to 121.68 kilograms compared to the original K-5's 136 kilograms, a weight reduction of approximately 10.5 percent that significantly improved tactical mobility without compromising structural integrity or operational performance.

The Type 63 reverse engineering effort also replicated the K-5's trolley-type two-wheeled motorized tow frame, designated the T76 120-mm mortar tow frame in Republic of China service. This transport system allows the mortar to be towed behind light vehicles, rapidly repositioned during tactical operations, and quickly brought into action or withdrawn when required. The combination of reduced weight and efficient transport system enhanced the weapon's utility for the Republic of China Army's operational concepts, which emphasized mobile defense and rapid repositioning to counter numerically superior People's Liberation Army forces.

Israeli Design Evolution and Comparative Development

While Taiwan successfully copied the K-5 design as it existed in the mid-1970s, Israel continued developing its mortar technology substantially beyond the baseline configuration that Taiwan had acquired through reverse engineering. After Israel purchased technical data from Finland, Israeli engineers improved the design according to their national operational requirements and combat experience. The original Israeli K-5 gradually evolved toward heavier weight and longer range configurations. The Israelis improved the tripod mounting and developed enhanced ammunition types, resulting in the heavier M-65 variant and the more capable K-6 model with a more complete variety of ammunition options. These developments not only improved firing angle flexibility and overall range performance, but also increased maximum effective range to 9,500 meters in the most capable configurations.

The K-6 model, which represents an updated version of the K-5 with a maximum range of 7,200 meters compared to the K-5's 6,200-meter range, incorporated a reinforced barrel that the manufacturer specifically recommends when firing long-range M57 ammunition. This barrel strengthening allows the weapon to safely withstand the higher chamber pressures associated with extended-range projectiles. The K-6 design proved successful enough that it was adopted by the U.S. Army as the M120/121 mortar system. Both the K-5 and K-6 can fire any type of qualified 120-mm shell in use worldwide, providing ammunition flexibility across NATO and other standardized inventories. The Iranian Hadid 120-mm HM16 mortar appears to be a very close copy of the K-6, indicating the design's proliferation beyond its original Israeli developers.

In contrast to Israel's continued development program, the Type 63 has been in service for over 30 years without significant improvements in range and accuracy. This stagnation reflects the fundamental limitation of Taiwan's approach: while Factory 61 successfully replicated the physical hardware, the absence of access to Israel's evolving technical data, ammunition development programs, and systems integration knowledge prevented Taiwan from pursuing parallel capability enhancements. The reverse engineering approach provided an immediate solution to Taiwan's heavy mortar requirements but created long-term capability gaps as the original design continued evolving in Israeli service.

Integration Challenges and Operational Limitations

Although Factory 61 completed the mass production tasks assigned by military leadership, this approach of copying hardware without complete systems integration revealed significant shortcomings in the arsenal's research and development capabilities for artillery systems. The most critical deficiency involved the absence of proper firing tables, which are essential for translating target location data into the specific elevation and azimuth settings required for accurate indirect fire. Lei Ying, who served as deputy commander of joint logistics, stated bluntly in his memoirs that "the Type 63 copied by Factory 61 was not even supplied with firing tables when distributed to troops, and units simply did not know how to shoot effectively." This fundamental gap in supporting documentation meant that crews lacked the mathematical tools to employ the weapon to its full potential, severely degrading the system's operational utility despite satisfactory hardware performance.

This practice of engaging in only a partial technology transfer prevented the Republic of China Army from fully replacing the U.S.-supplied M30 4.2-inch mortar (designated Type 62 4.2-inch mortar, or 4.2 heavy mortar in Republic of China service) in terms of infantry heavy fire support capabilities. In addition to the lack of firing tables, the quality of domestically produced ammunition and the smooth-bore design characteristic of the Type 63 made it impossible for the 120-mm mortar to match the shooting accuracy of rifled American-made mortars. The M30's rifled barrel imparts spin stabilization to projectiles, significantly improving accuracy and consistency compared to fin-stabilized ammunition fired from smooth-bore tubes. These accuracy limitations, combined with the documentation deficiencies, caused the Republic of China Army to maintain a low initial opinion of the 120-mm mortar's operational effectiveness despite its greater explosive payload compared to the 4.2-inch system.

The ultimate solution to these supporting system defects required Taiwan to reverse course and purchase artillery shells and related technical data from the original Israeli manufacturer, Soltam Ltd., effectively paying for the very technical information that Factory 61 had attempted to avoid acquiring through reverse engineering. The specific costs of these purchases remain classified, with no official data released regarding how much money was ultimately spent to rectify the deficiencies in the original reverse engineering program. The supporting system defects meant that troops equipped with the Type 63 in the early operational period could only achieve satisfactory performance when using Israeli-manufactured shells, creating a dependency on foreign ammunition supply that undermined the self-sufficiency goals that had motivated the reverse engineering approach in the first place.

Operational Evolution and Current Status

Even though the Type 63 entered service in the Republic of China military for a prolonged period, resolving the supporting system problems required considerable time and sustained effort. It was not until the early 1990s, when the Army's Type 62 4.2-inch mortar experienced multiple accidents that raised safety concerns, that military leadership was forced to accelerate the replacement of the U.S.-made heavy mortars. As the older 4.2-inch systems were mothballed or retired from active service, the Type 63 finally became the primary weapon for infantry heavy fire support in battalion-level units. This transition occurred not because the Type 63 had achieved full capability parity with the weapon it replaced, but because the alternative system had become operationally unsafe and politically untenable to continue operating.

In current Republic of China military service, the Type 63 mortar is deployed across multiple force structures and configurations. Reserve units and a small number of garrison units on outer islands continue to employ detachable Type 63 mortars in the traditional towed configuration, where the weapon is broken down into components and transported by vehicle or helicopter before being assembled at the firing position. Most mechanized infantry units operate the Type 63 mounted on CM22 120-mm mortar vehicles, which provide armor protection for the crew, enhanced mobility for rapid repositioning, and integrated fire control systems that partially compensate for the earlier deficiencies in firing data computation. A small number of units have mounted the Type 63 on V-150 armored vehicles for similar purposes, adapting the weapon to whatever vehicle platforms were available in inventory. Military police units have dismantled Type 63 mortars and carried them on medium-sized tactical wheeled vehicles, providing these security forces with heavy fire support capabilities for specialized missions.

The Type 63's sustained service across multiple decades, despite its troubled development history and initial operational limitations, reflects both the weapon's fundamental utility and the Republic of China military's constraints in replacing it with more advanced systems. The 120-mm caliber provides substantial explosive effects and range compared to lighter mortars, while the system's relative simplicity and Taiwan's indigenous production capability ensure sustainable logistics support. However, the weapon's performance remains constrained by its 1970s-era design origins and the continued accuracy limitations inherent in smooth-bore, fin-stabilized ammunition. Modern mortars incorporate advanced fire control computers, automated laying systems, and precision-guided munitions that the Type 63 lacks, gradually widening the capability gap between Taiwan's battalion-level indirect fire assets and those of potential adversaries. Whether Taiwan will invest in developing an entirely new heavy mortar system, procure foreign designs under license, or continue incremental upgrades to the Type 63 platform remains unclear, though budgetary pressures and competing modernization priorities in other capability areas may perpetuate the Type 63's service for the foreseeable future.