Munitions

Composition B

Also known as
  • Comp B
  • Composition B explosive

Composition B is a castable RDX/TNT military explosive mixture used as a high-explosive filler rather than as a standalone weapon. U.S. Army technical material describes a British formula transferred to the United States in 1940, then documents melt-cast processing, grade distinctions, density, and detonation data. Cataloged munitions such as the M107 projectile, M933A1 mortar cartridge, M888 mortar cartridge, M106 projectile, and 76mm HE-T M330 show how the filler appears inside shells, mortar rounds, and fixed ammunition.

Composition B, RDX/TNT melt-cast explosive filler, Munitions
Image source: Composition B Production Line 9 drawing
Profile / Specs

Profile

Origin
United Kingdom / United States
Built in
Canada
Type
RDX/TNT melt-cast explosive filler
Service note
World War II-era explosive composition that remained a standard fill for bombs, shells, and other military munitions
Designer
British explosive formula with U.S. wartime development and production programs
Designed
World War II era
Produced
World War II era and postwar production
Number built
Produced as bulk explosive filler and loaded into multiple munition families

Specifications

Composition
Army technical material lists Composition B at about 59.5 percent RDX and 39.5 percent TNT with tolerances; GAO rounds the inventory description to 60 percent RDX and 40 percent TNT.
Function
Used as a high-explosive filler in military munitions rather than as a standalone fired weapon.
Development path
Army technical material says the British formula was provided to the United States in 1940, followed by U.S. wartime development and large-scale production work.
Processing
Army technical material describes melting TNT at about 100 C, adding water-wet RDX with stirring, driving off moisture, adding wax where applicable, and then casting directly into munitions or solidifying chips for storage and shipment.
Grades
Army technical material separates standard Composition B from grade-specific formulations, including Composition B3 with Class F RDX and separate sensitivity-test discussion.
Detonation velocity
Army technical material lists Composition B at 1.68 g/cm3 with a detonation rate of 7,840 m/s, and lists Composition B2 at 1.72 g/cm3 with a detonation rate of 7,900 m/s.
Handling
Army technical material describes Composition B sensitivity as generally between TNT and RDX, with cast material more sensitive than powdered material.
Representative filled munitions
Source-backed catalog links include M107 155 mm projectiles, M933A1 120 mm mortar cartridges, M888 60 mm mortar cartridges, M106 203 mm projectiles, and 76mm HE-T M330 rounds.
Authorized Canadian listing
A Canadian authorized-explosives list names Composition B under Expro Chemical Products / Produits Chimiques Expro of Valleyfield, Quebec.
Variants

Public explosive references distinguish standard Composition B from grade-specific formulations. The page keeps those formulations as composition variants, not separate fired weapons.

VariantConfigurationDesignation notes
Composition B3grade / formulation variant

Army technical material lists Composition B3 as a related Composition B family grade using Class F RDX, with separate composition and sensitivity data.

Sources: TM 9-1300-214 Military Explosives

Munitions Loaded With Composition B

These cataloged rounds and projectiles have source-backed Composition B filler statements. The links identify filler relationships only; they do not make Composition B itself a directly documented conflict-use entry.

Compatible itemItem typeCompatibility evidence
M107 155 mm high-explosive projectile, 155 mm high-explosive projectile, ArtilleryM107 155 mm high-explosive projectile155 mm high-explosive projectile

General Dynamics describes the M107 as a forged-steel 155 mm projectile filled with Composition B high explosive, and the Army portfolio also lists M107 variants in the 155 mm ammunition set.

Sources: 155mm M107 HE, JPEO Ammunition Portfolio Book 2017

M933-series mortar projectile, 120mm high-explosive mortar cartridge, ArtilleryM933-series mortar projectile120 mm high-explosive mortar cartridge

General Dynamics and Day & Zimmermann both describe M933A1-series 120 mm HE mortar cartridges as steel projectiles loaded with Composition B or Comp B explosive.

Sources: 120MM M933A1 HE, Day & Zimmermann M933A1 M934A1 product sheet

M888 60 mm high explosive cartridge, 60 mm high-explosive mortar cartridge, MunitionsM888 60 mm high explosive cartridge60 mm high-explosive mortar cartridge

Army and environmental ordnance references identify the M888 as a 60 mm HE cartridge for M224-series mortars; the cataloged round records Composition B as its explosive fill.

Sources: JPEO Ammunition Portfolio Book 2017, EPA AP-42 Cartridges 30-75 mm

M106 203 mm high-explosive fragmentation projectile, 203 mm high-explosive fragmentation projectile, MunitionsM106 203 mm high-explosive fragmentation projectile203 mm high-explosive fragmentation projectile

The M106 projectile record is linked here because specialist munition data identifies the 8-inch HE-fragmentation projectile with TNT or Composition B filling.

Sources: M106 (US 8" HE Projectile)

76mm HE-T M330, 76 mm high-explosive tracer round, Munitions76mm HE-T M33076 mm high-explosive tracer round

Nexter's ammunition catalog lists the M330 projectile with a 0.7 kg Composition B filling in the Saladin and Scorpion 76 mm ammunition family.

Sources: Nexter 2016 Catalog

Filler Scope

Composition B remains a relationship-only support page because the available sources document explosive composition and filler relationships, while conflict-use evidence belongs to the complete munition records.

Sources: TM 9-1300-214 Military Explosives, 155mm M107 HE, 120MM M933A1 HE

Composition And Filler Context

Composition B is best read as a filler material inside complete munitions. The technical sources support its RDX/TNT composition and melt-cast processing, while the relationship links show specific cataloged rounds where public sources identify the filler.

Mixture

Army technical material lists Composition B at about 59.5 percent RDX and 39.5 percent TNT, while GAO rounds the inventory description to a 60/40 RDX/TNT mixture.

Processing

Army technical material describes melting TNT, adding water-wet RDX, driving off moisture, and casting the mixture directly into munitions or into chips for storage and shipment.

Page scope

The record links filler relationships to complete munitions but keeps conflicts empty because the explosive composition is not independently documented as the conflict-used item.

Sources: Defense Inventory: Production, Distribution, and Storage of C-4 Explosive; TM 9-1300-214 Military Explosives; 155mm M107 HE; 120MM M933A1 HE; Nexter 2016 Catalog.

Related Weapon Systems
M888 60 mm high explosive cartridge, 60 mm high-explosive mortar cartridge, MunitionsMunitionsM888 60 mm high explosive cartridge60 mm high-explosive mortar cartridgeThe M888 is a U.S. 60 mm high-explosive mortar cartridge for the M224/M224A1 Lightweight Company Mortar System. Army and environmental ordnance references identify it as DODIC B643 with an M935 point-detonating fuze, Composition B fill, 67- to 3,490-meter range, and fragmentation/blast effects against personnel and light materiel. Public conflict-specific evidence for this cartridge currently comes from Afghan National Army and Iraq Train and Equip Fund supply records, so the conflict rows document transfer and delivery context rather than confirmed battlefield firing.
M106 203 mm high-explosive fragmentation projectile, 203 mm high-explosive fragmentation projectile, MunitionsMunitionsM106 203 mm high-explosive fragmentation projectile203 mm high-explosive fragmentation projectileThe M106 is a U.S. 8-inch, or roughly 203 mm, high-explosive fragmentation projectile built for American heavy artillery such as the M110. Open munition references describe a nose-fuzed, boat-tailed steel shell with TNT or Composition B filling, while Ukrainian and defense-reporting sources document M106 projectiles being adapted to Ukrainian 2S7 Pion guns during the 2014 Russia-Ukraine War as Soviet-pattern 203 mm stocks became scarce.
76mm HEP-T M329, 76 mm fixed HESH-T / HEP-T tank-gun round, MunitionsMunitions76mm HEP-T M32976 mm fixed HESH-T / HEP-T tank-gun roundThe 76mm HEP-T M329 is a MECAR high-explosive squash head service round for the British L5A1 and L23/L23A1 76 mm gun family used on Saladin and Scorpion vehicles. Nexter's 2016 ammunition catalog lists it as an in-service fixed HESH-T round for personnel, bunkers, light armour, structures, and other material targets, with a Composition A3-filled projectile, base-detonating graze fuze, M23 tracer, and 533 m/s nominal muzzle velocity.

Sources

Canadian Authorized Explosives ListPublisher: Natural Resources Canada | Note: Archived copy of Canada's authorized explosives list; supports Expro Chemical Products / Produits Chimiques Expro of Valleyfield as the listed company for Composition B and Composition C-4. | Accessed: 2026-07-13Insensitive melt cast explosive compositions patentPublisher: Google Patents | Note: Supports Canadian defence-research context and states that Composition B used in the examples was obtained from Expro Chemical Products. | Accessed: 2026-07-13Defense Inventory: Production, Distribution, and Storage of C-4 ExplosivePublisher: U.S. Government Accountability Office | Note: Supports Composition B composition and the statement that it was used as an explosive filler in multiple items. | Accessed: 2026-07-13TM 9-1300-214 Military ExplosivesPublisher: U.S. Environmental Protection Agency | Note: EPA-hosted copy of the U.S. Army technical manual; supports Composition B development background, manufacture, casting, stability, density, detonation velocity, handling, and variant details. | Accessed: 2026-07-13155mm M107 HEPublisher: General Dynamics Ordnance and Tactical Systems | Note: Supports the relationship between Composition B and the M107 155 mm projectile by identifying the projectile as filled with Composition B high explosive. | Accessed: 2026-07-13120MM M933A1 HEPublisher: General Dynamics Ordnance and Tactical Systems | Note: Supports the relationship between Composition B and the M933A1 120 mm HE cartridge by describing its steel shell body with Composition B fill. | Accessed: 2026-07-13Day & Zimmermann M933A1 M934A1 product sheetPublisher: Day & Zimmermann | Note: Supports the relationship between Composition B and the M933A1/M934A1 mortar-cartridge family by stating that the HE steel projectiles are loaded with Comp B explosive. | Accessed: 2026-07-13JPEO Ammunition Portfolio Book 2017Publisher: U.S. Army Capability Program Executive Ammunition & Energetics | Note: Supports U.S. Army ammunition context for Composition B-filled cartridge and projectile families, including M107 and M888-related portfolio entries. | Accessed: 2026-07-13EPA AP-42 Cartridges 30-75 mmPublisher: U.S. Environmental Protection Agency | Note: Supports environmental ordnance data for 30-75 mm cartridges, including the M888 60 mm HE cartridge context used for the filler relationship. | Accessed: 2026-07-13M106 (US 8" HE Projectile)Publisher: METIS - Fenix Insight | Note: Supports the relationship between Composition B and the M106 8-inch / 203 mm high-explosive fragmentation projectile by identifying TNT or Composition B filling. | Accessed: 2026-07-13Nexter 2016 CatalogPublisher: Internet Archive / Nexter | Note: Supports the relationship between Composition B and the 76mm HE-T M330 round by listing a 0.7 kg Composition B projectile filling. | Accessed: 2026-07-13Composition B Production Line 9 drawingPublisher: Wikimedia Commons | Note: Image provenance for a public-domain HAER / National Park Service drawing of Holston Army Ammunition Plant's RDX-and-Composition-B Manufacturing Line 9. | Accessed: 2026-07-13