13.2×99mm Hotchkiss Long

Lore & Background

The 13.2 × 99 mm Hotchkiss cartridge was developed in 1925 by the company Hotchkiss et Cie and the French Society of Ammunition as part of a longer development period to produce a modern heavy machine gun cartridge for the in-development 13.2 mm Hotchkiss machine gun. By 1926 the new weapon entered production and quickly gained popularity. By 1935 the weapon and a license to produce it had been purchased by both Italy and Imperial Japan, becoming the Breda Model 1931 machine gun and Type 93 Heavy Machine Gun in each respective country.

Even though the cartridge saw massive success on the export market, the French military found it to wear out gun barrels too quickly and launched a project to revamp the cartridge. This eventually led to Hotchkiss replacing the design with a slightly shortened version in 1935, becoming the 13.2 × 96 mm Hotchkiss Short. This shortened version featured the same overall dimensions as the original cartridge but featured a slightly shortened neck and a reworked projectile shape, resulting in less wear on the gun barrel when firing. The introduction of this new design did not stop continued use and production of the 13.2×99 mm Hotchkiss Long cartridge by countries whom had already adopted it, and in 1939 the cartridge saw new interest on the export market due to the newly developed 13.2 mm FN Browning aircraft machine gun, which was offered in both 12.7 × 99 mm Browning and 13.2 × 99 mm Hotchkiss Long.

During WWII the 13.2 × 99 mm Hotchkiss cartridge saw major use in combat by both Allied and Axis forces, mainly being used in 13.2 mm Hotchkiss machine guns and its license produced derivatives. By the end of the war the cartridge started being superseded by the very similar 12.7 × 99 mm Browning cartridge as used in the spreading American .50 M2 Browning heavy machine gun, eventually leading to the death of both 13.2 mm Hotchkiss cartridges post war.

Reader's Guide

The 13.2 × 99 mm Hotchkiss Long cartridge is notable for its widespread adoption across multiple nations during the interwar period and World War II, serving as a heavy machine gun cartridge for both Allied and Axis forces. Its development in 1925 by Hotchkiss et Cie and the French Society of Ammunition produced a round that was quickly licensed by Italy and Japan, resulting in the Breda Model 1931 and Type 93 heavy machine guns. The cartridge's export success was significant, but the French military's concern over barrel wear led to a shortened variant in 1935, the 13.2 × 96 mm Hotchkiss Short, though the original Long cartridge continued in production and use by other nations. The cartridge gained renewed interest in 1939 with the FN Browning aircraft machine gun chambered for it. Its legacy is defined by its role in equipping numerous machine guns across different theaters of WWII, but it was ultimately superseded by the 12.7 × 99 mm Browning cartridge after the war, which became the NATO standard and led to the disappearance of the 13.2 mm Hotchkiss cartridges.

Did You Know?

• The 13.2 × 99 mm Hotchkiss Long is also known as the 13.2 Mle. 1930, 13.2 Breda, and 13.2 Japanese.
• By 1935, Italy and Imperial Japan had purchased licenses to produce the weapon, creating the Breda Model 1931 and Type 93 Heavy Machine Gun.
• A shortened variant, the 13.2 × 96 mm Hotchkiss Short, was introduced in 1935 to reduce barrel wear.

Development & Design Philosophy

In the 1920s, Hotchkiss et Cie set out to build a family of anti-aircraft automatic weapons spanning 13.2, 25, and 37 mm calibers, all sharing a common gas-operated action descended from the 8 mm Mle 1914 machine gun that had earned a reputation for reliability in the First World War. The 13.2 mm project specifically began in 1922 with the original intent of serving as an aircraft machine gun. However, the French government intervened: it classified the belt-fed variant and declined to fund its further development, effectively restricting the weapon to the magazine-fed configuration. Only this ground- and naval-use version was cleared for export, a process that began around 1927. Production continued through the late 1920s and into the 1930s, and the design attracted enough international interest that both Italy and Japan went on to manufacture the gun under license. The result was a heavy machine gun whose primary mission was close-range air defense, yet whose magazine-fed architecture and versatile mounting options gave it a broader operational life than its origins as an aircraft weapon might have suggested.

Cartridge Evolution & Rate-of-Fire Limits

The 13.2×99 mm Hotchkiss "Long" cartridge was, in essence, a 12.7×99 mm Browning .50 BMG round necked up to 13.2 mm caliber. While this gave the M1929 a powerful projectile, it came at a steep cost: barrel wear was severe enough that Hotchkiss felt compelled to introduce a revised round in 1935. The new 13.2×96 mm "Short" cartridge featured a slightly shorter case and a reworked projectile shape, reducing overall case length by just three millimeters. Crucially, the change was small enough that existing weapons and production lines required no modification to chamber it, yet it was sufficient to solve the barrel-erosion problem. On the performance side, the M1929's cyclic rate was rated at 450 rounds per minute, but the practical sustained rate fell to roughly 200–250 rounds per minute. The culprit was the overhead 30-round curved box magazine, which would be exhausted in approximately four seconds of continuous fire, forcing the gunner into frequent magazine changes that throttled the effective rate of fire well below the theoretical maximum.

Naval Service & International Adoption

The 13.2 mm Hotchkiss found perhaps its most widespread role as a naval close-in weapon. During the early years of the Second World War, French, Italian, and Japanese warships carried twin (designated CAD Mle 1929) and quadruple (CAQ Mle 1929) mountings for the gun. In Italy, Società Italiana Ernesto Breda produced a licensed version called the Breda Mod.31 beginning in 1931, which equipped ships, submarines, and armored trains of the Royal Italian Navy; after the war it continued in service on Guardia di Finanza patrol boats. The Spanish Navy acquired the weapon in December 1935 and mounted it on Republican destroyers and cruisers during the Civil War, with the Pirotecnia Militar plant in Sevilla producing cartridges from 1939 onward. Japanese license-produced guns also saw naval service. By 1943, however, the 13.2 mm was being superseded: French warships refitted in the United States, including the battleship Richelieu and the destroyer Le Terrible, had their Hotchkiss guns replaced by more powerful Oerlikon 20 mm cannons, marking the end of the cartridge's frontline naval career.

Ground, Armored, and International Variants

Beyond the deck, the M1929 served in a remarkable variety of ground and armored roles. French infantry commanders initially rejected the 13.2 mm for light anti-aircraft duty, arguing that heavy bullets falling from the sky posed a danger to friendly troops and preferring larger calibers with self-destructing shells. Nevertheless, the gun was adopted for French cavalry armored vehicles, the Belgian T15, the AMR 35 light tank, and the White-Laffly AMD 80 armoured car, as well as for static fortifications. In the 1930s, self-propelled anti-aircraft combinations on Citroën-Kegresse and Berliet chassis were tested but never mass-produced. Free French forces in North-East Africa in 1942 improvised self-propelled mountings using guns recovered from French ships. Italy mounted the Breda Mod.31 on command tanks and on L3/33 light tanks exported to Brazil. Japan fitted license-produced guns to Type 92 Heavy armored cars. Greece developed its own variant, fed by a rigid metal band rather than a box magazine, mounted on an articulated tripod for dual anti-aircraft and anti-tank use. Nazi Germany even designated captured French examples as MG 271(f).