Artillery

203 mm howitzer M1931 (B-4)

Also known as
  • 203mm B-4
  • 203mm B-4M
  • 203 mm B-4M
  • B-4 203 mm howitzer
  • B-4M
  • B-4M howitzer
  • M1931 B-4
  • 203 mm howitzer M1931
  • 203-mm howitzer M1931
  • 52-G-625
  • 52-G-625M
  • 203.4 mm B-4M
  • 20.3 cm Haubitze 503/5(r)
  • Stalin's sledgehammer

The 203 mm howitzer M1931 (B-4) was a Soviet high-power heavy howitzer built for reserve artillery, siege fire, bunker attack, and urban demolition, later modernized as the wheeled B-4M. Its 203 mm shell, slow rate of fire, and difficult transport made it a specialized weapon rather than a divisional howitzer, but sources document Soviet and captured German use during the Second World War, including prominent employment in the Battle of Berlin.

203 mm howitzer M1931 (B-4), 203 mm tracked heavy howitzer, Artillery
Image source: Wikimedia Commons 3rd Belorussian Front B-4 image

Role in Conflicts

Profile / Specs

Profile

Origin
Soviet Union
Type
203 mm tracked heavy howitzer
Service note
Designed in 1931, produced during the 1930s and early 1940s, and fielded as Soviet heavy artillery during the Second World War.
Designer
Bolshevik Plant / Soviet artillery design program
Designed
1931 design; adopted for service in the mid-1930s
Produced
1932-1942 in the principal open-source production account
Number built
About 800-1,010 examples depending on source and counting method

Specifications

Caliber
203 mm / 8-inch class
Configuration
Towed heavy howitzer on a tracked, non-self-propelled carriage
Combat weight
About 17,700 kg
Crew
15
Projectile weight
About 98.5-100 kg high-explosive projectile; heavier concrete-piercing projectiles also reported
Ammunition type
Bag-type, variable-charge separate loading
Maximum range
About 18 km / roughly 20,000 yards depending on source and ammunition
Muzzle velocity
About 606-607 m/s for full-charge high-explosive fire
Rate of fire
Slow; GlobalSecurity gives 0.5-1 round per minute and WW2DB gives 1 round per minute
Elevation and traverse
0 to +60 degrees elevation; about 8 degrees traverse
Breech and recoil
Screw-type breechblock with hydraulic / hydropneumatic recoil system
B-4M carriage
Postwar four-wheel carriage accepted in 1955, with wheels raised off the ground in firing position
B-4M towing vehicle
AT-T heavy artillery tractor
B-4M towing speed
About 30 km/h in the WeaponSystems.net profile, compared with lower road speed for the tracked wartime carriage
Tracked Heavy-Howitzer Design

The B-4's tracked carriage was unusual for a towed artillery piece: it was not self-propelled, but it spread weight and improved movement over rough or soft ground. The same design choice also made long movement cumbersome, since early guns could require separate tube transport. Postwar B-4M conversions kept the 203 mm ordnance but moved it to a wheeled carriage for road towing.

Wartime carriage

Tracked, towed carriage for the M1931 B-4, with no engine of its own and limited road-march convenience.

Sources: U.S. Army Field Artillery Museum B-4 article; GlobalSecurity B-4 profile.

B-4M carriage

Four-wheel postwar carriage; the wheels were raised for firing and the weapon rested on its firing platform.

Sources: GlobalSecurity B-4 profile; U.S. Army FM 100-2-3 Soviet Army equipment manual.

Fire mission

Reserve heavy artillery for fortifications, urban strongpoints, and other targets where a 203 mm shell mattered more than mobility or rate of fire.

Sources: U.S. Army Field Artillery Museum B-4 article; World War II Database B-4 profile.

Transport change

The B-4M modernization addressed long-distance movement with AT-T tractor towing and a carriage that avoided removing the tube for routine travel.

Sources: GlobalSecurity B-4 profile; U.S. Army FM 100-2-3 Soviet Army equipment manual.

Ammunition And Projectiles

The B-4 used separate-loading, variable-charge ammunition rather than a fixed cartridge. Accessible sources agree on a roughly 98.5-100 kg high-explosive projectile and also describe heavier concrete-piercing ammunition for hardened targets, which fits the weapon's reserve-artillery and siege role.

Loading system

Bag-type, variable-charge separate loading, with the projectile and propellant handled separately.

Sources: U.S. Army FM 100-2-3 Soviet Army equipment manual; GlobalSecurity B-4 profile.

High explosive

U.S. Army and World War II Database references place the standard HE projectile in the 98.5-100 kg class.

Sources: U.S. Army FM 100-2-3 Soviet Army equipment manual; World War II Database B-4 profile.

Concrete targets

GlobalSecurity lists concrete-piercing projectiles as a main ammunition type and gives a 146 kg concrete-piercing shell weight.

Source: GlobalSecurity B-4 profile.

Range context

The same source set places maximum range around 18 km, with exact figures varying by projectile, charge, and reference.

Sources: U.S. Army FM 100-2-3 Soviet Army equipment manual; GlobalSecurity B-4 profile; World War II Database B-4 profile.

Variants

The B-4 family is most often divided by carriage: the wartime tracked M1931 carriage and the postwar B-4M wheeled modernization.

VariantConfigurationDesignation notes
M1931 B-4 tracked carriageOriginal high-power howitzer

The original B-4 used a tracked, towed carriage that could move over poor roads and soft ground but had no engine of its own.

Sources: U.S. Army Field Artillery Museum B-4 article, GlobalSecurity B-4 profile

B-4MPostwar wheeled-carriage modernization

The B-4M was a 1955 wheeled-carriage modernization rather than a newly produced gun: sources describe refurbished B-4 ordnance mounted on a four-wheel carriage, with the wheels raised for firing and AT-T tractor towing for road moves.

Sources: GlobalSecurity B-4 profile, WeaponSystems.net B-4M profile

S-51Experimental self-propelled mounting

The S-51 was a wartime experimental mounting of the B-4 gun on a KV-1S tank chassis; recoil and vehicle damage problems kept it from series production.

Sources: Wikipedia B-4 baseline

Timeline

203 mm howitzer M1931 (B-4) Key Events

  1. B-4 design completed

    Open sources describe the M1931 B-4 as a 203 mm Soviet howitzer designed in 1931.

    Sources: U.S. Army Field Artillery Museum B-4 article, GlobalSecurity B-4 profile

  2. Production begins

    Reference accounts place production start in 1932, with Bolshevik Plant and Barrikady among the named producers.

    Sources: GlobalSecurity B-4 profile, Wikipedia B-4 baseline

  3. Captured guns enter German service

    The Fort Sill museum article describes its displayed B-4 as captured by Germany from Soviet forces in 1941 and then used against Soviet forces during the war.

    Sources: U.S. Army Field Artillery Museum B-4 article

  4. Berlin urban fire missions

    Museum and reference accounts describe Soviet B-4 howitzers used in the Battle of Berlin to demolish German-occupied buildings and strongpoints.

    Sources: U.S. Army Field Artillery Museum B-4 article, World War II Database B-4 profile

  5. B-4M test carriages prepared

    B-4M accounts describe two prototype wheeled carriages, fitted with B-4 and Br-2 ordnance, being sent for tests in December 1954 after the carriage project was completed earlier that year.

    Sources: WeaponSystems.net B-4M profile, Wikipedia B-4M baseline

  6. B-4M enters service

    The wheeled B-4M carriage was accepted in 1955, giving the B-4 family a postwar towing configuration better matched to the AT-T artillery tractor.

    Sources: WeaponSystems.net B-4M profile, Wikipedia B-4M baseline

Media

203 mm howitzer M1931 (B-4) Images

203 mm howitzer M1931 (B-4), 203 mm tracked heavy howitzer, Artillery - view 1
Source: Wikimedia Commons Aberdeen B-4 museum image
203 mm howitzer M1931 (B-4), 203 mm tracked heavy howitzer, Artillery - view 2
Source: Wikimedia Commons B-4M Saint Petersburg image
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Sources

U.S. Army Field Artillery Museum B-4 articlePublisher: U.S. Army | Note: Supports Second World War direct conflict use by documenting the B-4 used by Soviet forces as heavy artillery, used by German forces after capture, and used in the Battle of Berlin urban demolition role; also supports identity, caliber, carriage context, range summary, and Fort Sill museum provenance. | Accessed: 2026-07-13GlobalSecurity B-4 profilePublisher: GlobalSecurity.org | Note: Supports Second World War direct conflict use by documenting B-4 howitzers fielded by Soviet heavy artillery and used by captured German units; also supports development, Bolshevik Plant and Barrikady production attribution, B-4M carriage distinction, ammunition, transport notes, and specifications. | Accessed: 2026-07-13U.S. Army FM 100-2-3 Soviet Army equipment manualPublisher: U.S. Department of the Army | Note: Supports B-4 and B-4M technical context, including carriage types, tube removal for long moves, AT-T towing, separate-loading variable-charge ammunition, projectile weight, range, rate of fire, and replacement by the 2S7. | Accessed: 2026-07-13World War II Database B-4 profilePublisher: World War II Database | Note: Supports Second World War direct conflict use by documenting B-4 howitzers used by Soviet forces against German fortifications during the advance toward Berlin; also supports dimensions and performance figures. | Accessed: 2026-07-13Wikipedia B-4 baselinePublisher: Wikipedia | Note: Baseline terminology and leads for aliases, GRAU index, production figures, S-51 experimental variant, and ammunition-family context; claims are cross-checked where possible against stronger sources. | Accessed: 2026-07-13WeaponSystems.net B-4M profilePublisher: WeaponSystems.net | Note: Supports B-4M identity, 1955 service entry, OKB-221 and Barrikady development context, conversion rather than new-build status, wheeled carriage details, AT-T towing context, and B-4M-specific specifications. | Accessed: 2026-07-13Wikipedia B-4M baselinePublisher: Wikipedia | Note: Baseline terminology and leads for the B-4M GRAU index, 1954-1955 carriage modernization chronology, OKB-221 and Barrikady context, and reported Russian storage figures; used as a secondary lead rather than the sole source for core claims. | Accessed: 2026-07-13Wikimedia Commons 3rd Belorussian Front B-4 imagePublisher: Wikimedia Commons | Note: Supports Second World War direct conflict use by showing a B-4 howitzer used by the Soviet 3rd Belorussian Front in 1944; also supports reusable primary image provenance. | Accessed: 2026-07-13Wikimedia Commons Aberdeen B-4 museum imagePublisher: Wikimedia Commons | Note: Supports reusable gallery image provenance for a B-4 photographed at the United States Army Ordnance Museum, licensed CC BY-SA 2.5 by the uploader. | Accessed: 2026-07-13Wikimedia Commons B-4M Saint Petersburg imagePublisher: Wikimedia Commons | Note: Supports reusable gallery image provenance for a B-4M photographed at the Saint Petersburg Artillery Museum and released into the public domain by the uploader. | Accessed: 2026-07-13