M42 Dual-Purpose Improved Conventional Munition (DPICM) Submunition
1. Overview
The M42 is an artillery-delivered anti-personnel/anti-materiel submunition designed to engage both personnel and lightly armored vehicles through combined shaped charge and fragmentation effects. As one of the primary payloads in US Dual-Purpose Improved Conventional Munition (DPICM) artillery projectiles, the M42 provides field artillery with an area-effect capability against troops, vehicles, and equipment. The submunition combines a small shaped charge capable of penetrating light armor with a fragmenting body for anti-personnel effects.
2. Country/Bloc of Origin
- Country: United States of America
- Developer: US Army / Various defense contractors
- Development Period: 1970s
- Service Entry: 1975
- International Users: United States and numerous NATO/allied nations
The M42 was developed as part of the US Army’s effort to provide conventional artillery with improved effectiveness against the massed armor and mechanized infantry formations expected in a NATO-Warsaw Pact conflict.
3. Ordnance Class
| Attribute | Classification |
|---|---|
| Type | Submunition / Bomblet / Grenade |
| Role | Dual-Purpose (Anti-Personnel and Anti-Materiel) |
| Delivery Method | Artillery-delivered via cargo projectile |
| Category | Improved Conventional Munition (ICM) |
| Target Types | Personnel, light armor, trucks, equipment |
The M42 is classified as a DPICM (Dual-Purpose Improved Conventional Munition) submunition, indicating its effectiveness against both “soft” targets (personnel) and “hard” targets (light armor/vehicles).
4. Ordnance Family / Nomenclature
Primary Designation:
- M42 (Grenades, Submunition)
- M46 (Companion anti-tank submunition in same projectile family)
Parent Projectiles:
- M483A1 – 155mm DPICM projectile containing 88 submunitions (64 M42, 24 M46)
- M864 – 155mm Base Bleed DPICM with extended range
- M449/M449A1 – 155mm ICM projectiles (earlier variants)
Related Munitions:
- M46 – Larger anti-tank shaped charge submunition (same projectile family)
- M77 – MLRS DPICM submunition (similar function)
- M85 – German/international DPICM submunition (similar design)
NATO Designation: The M42/M46 system is standard across NATO forces using US-origin DPICM.
Common Names:
- DPICM Grenade
- ICM Bomblet
- “Bomblet” (general term)
5. Hazards
Primary Hazards
| Hazard Type | Description |
|---|---|
| Shaped Charge | Armor-penetrating jet for anti-materiel effect |
| Fragmentation | Steel body fragments at high velocity |
| Score Pattern | Pre-scored case creates optimized fragmentation |
Dual-Purpose Effectiveness
The M42’s design creates complementary effects:
- Shaped charge penetrates light armor, engine blocks, equipment
- Fragmentation produces casualties among exposed personnel
- Combined effect damages vehicles while suppressing/killing crews
Sensitivity Factors
- Impact Fuze: All-ways acting, functions on impact; duds retain sensitivity
- Ribbon Tangling: Stabilization ribbon can snag on vegetation, causing erratic behavior
- Dud Rate: Historical dud rates of 5-15%+ create significant UXO hazard
- Fuze State: Armed duds may function if subsequently disturbed
Safety Considerations
- High Dud Rate: Artillery-delivered submunitions historically have high dud rates
- Wide Dispersal: Large area coverage means extensive UXO contamination potential
- Small Size: Can be partially buried, concealed in debris, or picked up
- Delayed Hazard: Duds may function days, months, or years later if disturbed
- Multiple Hazards: Both explosive and fragmentation effects
Kill/Danger Radius
| Zone | Distance | Effect |
|---|---|---|
| Lethal Radius | ~10 meters (individual bomblet) | Fatal injuries likely |
| Casualty Radius | ~20 meters | Fragmentation injury risk |
| Pattern Coverage | Variable | Depends on projectile burst height/angle |
| Safety Distance | Minimum 50 meters | From individual dud |
⚠️ WARNING: M42 submunitions have historically high dud rates. Unexploded bomblets may be partially buried, hidden in vegetation, or covered by debris. The all-ways acting fuze may detonate if the bomblet is touched, moved, or disturbed. Never approach any suspected M42 munition.
6. Key Identification Features
Physical Characteristics
| Dimension | Measurement |
|---|---|
| Length | Approximately 8.5 cm (3.3 inches) |
| Diameter | Approximately 3.8 cm (1.5 inches) |
| Weight | Approximately 215 grams (7.6 oz) |
Visual Identification
- Shape: Cylindrical body with hemispherical nose and ribbon tail
- Color: Olive drab (OD) green body
- Markings: May have yellow band indicating HE content
- Material: Steel body with pre-scored fragmentation pattern
- Distinctive Features:
- Nylon stabilization ribbon (may be extended or tangled)
- Hemispherical nose section (shaped charge)
- Pre-scored fragmentation grooves on body
- Small size relative to other bomblets
Stabilization Ribbon
The M42 uses a nylon ribbon for stabilization:
- Deploys upon ejection from projectile
- Orients bomblet nose-down during descent
- Ribbon may be found extended, tangled, or wrapped around objects
- Ribbon itself can indicate presence of submunition in area
Pre-Scored Fragmentation
The M42 body features external scoring:
- Grooves machined into steel case
- Controls fragmentation pattern upon detonation
- Creates uniform, optimized fragment size
- May be visible as parallel lines on body
Condition Indicators
- Intact: OD green body visible, ribbon may be deployed
- Partially Functioned: Damaged body, deformation, partial fragmentation
- Dud: Appears intact but impacted without detonating; extremely dangerous
- Buried/Concealed: May be partially underground or hidden in debris
7. Fuzing Mechanisms
Primary Fuze System
The M42 employs an all-ways acting (AWA) piezoelectric impact fuze:
| Component | Function |
|---|---|
| Piezoelectric Element | Generates firing current on impact |
| All-Ways Acting Mechanism | Enables function at any impact angle |
| Firing Circuit | Initiates detonator |
| Detonator | Primary explosive initiation |
Arming Sequence
- Ejection: Projectile base expels submunitions at preset altitude
- Ribbon Deployment: Nylon ribbon pulls free, creating drag
- Orientation: Ribbon stabilizes bomblet, orients nose-down
- Spin-Up/Arming: Rotation and/or setback arms fuze
- Descent: Bomblet falls toward target
- Impact: Piezoelectric fuze generates current, initiates detonation
Safety Mechanisms
- Setback Safety: Requires acceleration of ejection
- Centrifugal/Mechanical Safety: Additional arming requirement
- All-Ways Acting: Designed to function regardless of impact angle
Piezoelectric Fuze Operation
The piezoelectric fuze uses crystal element that generates electrical current when subjected to mechanical stress:
- Impact shock creates current
- Current fires detonator
- No battery required
- Extremely reliable when functioning properly
Dud Fuze Conditions
Unexploded M42 submunitions may have fuzes in various states:
- Unarmed Dud: Failed to complete arming (still dangerous)
- Armed Dud: Fully armed but failed impact function (extremely dangerous)
- Delayed Function Risk: May detonate with any subsequent disturbance
Common Dud Causes
- Soft impact surface (mud, sand, snow, vegetation)
- Fuze malfunction
- Ribbon entanglement affecting orientation
- Low ejection altitude
- Manufacturing defects
8. History of Development and Use
Development Background
The M42 DPICM submunition emerged from 1970s efforts to improve artillery effectiveness against mechanized forces. Traditional high-explosive artillery was inefficient against dispersed armored formations—the DPICM concept addressed this by creating hundreds of small lethal areas across the target zone.
Development Timeline
| Year | Event |
|---|---|
| 1970s | DPICM concept development |
| 1975 | M42 enters US Army service |
| 1980s | Widespread NATO adoption |
| 1991 | Extensive use in Operation Desert Storm |
| 2003 | Used in Iraq War |
| 2008 | Convention on Cluster Munitions (US did not sign) |
| 2017+ | US policy changes on DPICM use |
Tactical Employment
DPICM became a fundamental artillery capability:
Typical Missions:
- Suppression of enemy air defenses (SEAD support)
- Counter-battery fire against artillery positions
- Engagement of armored/mechanized formations
- Interdiction of road networks and chokepoints
- Destruction of soft targets and equipment
Fire Planning:
- Multiple projectiles fired to create dense patterns
- Battalion and brigade artillery masses DPICM fires
- Time-on-target missions for simultaneous impact
Combat Use
Operation Desert Storm (1991): US and coalition artillery fired massive quantities of DPICM against Iraqi positions:
- Artillery positions suppressed and destroyed
- Armored formations engaged during ground offensive
- Significant unexploded ordnance left in theater
Operation Iraqi Freedom (2003): DPICM employed against Iraqi military targets:
- Post-conflict UXO clearance challenges
- Civilian casualties from unexploded bomblets
Controversy and Policy Changes
DPICM has faced increasing criticism:
- Dud Rates: Actual field dud rates significantly higher than specifications
- Civilian Casualties: Post-conflict UXO kills and injures civilians
- Environmental Contamination: Large areas rendered hazardous
- 2008 CCM: Convention on Cluster Munitions (US did not sign)
- US Policy Evolution:
- 2008 DOD policy requiring <1% dud rate
- Subsequent policy reviews and restrictions
- 2022 policy change permitting transfer to Ukraine
Current Status
- M42 DPICM remains in US inventory
- Subject to evolving policy restrictions
- Significant existing UXO contamination in past conflict zones
- Ongoing debate over military utility vs. humanitarian concerns
9. Technical Specifications
Explosive Content
| Specification | Detail |
|---|---|
| Main Charge | Composition A5 or similar |
| Charge Weight | Approximately 21 grams (0.74 oz) |
| Shaped Charge Liner | Copper |
Warhead Effects
| Effect Type | Capability |
|---|---|
| Shaped Charge Penetration | ~65mm (2.5 inches) RHA |
| Fragmentation | High-velocity steel fragments |
| Effective Range | ~10m lethal radius |
Performance Characteristics
| Specification | Detail |
|---|---|
| Armor Penetration | 65mm Rolled Homogeneous Armor |
| Effective Against | Personnel, APCs (top/side), trucks, equipment |
| Function Mode | Impact (all-ways acting piezoelectric) |
| Stabilization | Nylon ribbon drag |
Parent Projectile Configuration
| Projectile | M42 Count | M46 Count | Total |
|---|---|---|---|
| M483A1 (155mm) | 64 | 24 | 88 |
| M864 (155mm BB) | Similar configuration | Extended range | ~88 |
Comparison with M46
| Characteristic | M42 | M46 |
|---|---|---|
| Primary Role | Anti-personnel | Anti-tank |
| Armor Penetration | 65mm | 150mm+ |
| Size | Smaller | Larger |
| Quantity per Projectile | More numerous | Fewer |
10. Frequently Asked Questions
Q: What is the difference between the M42 and M46 submunitions? A: The M42 and M46 are complementary submunitions loaded together in DPICM projectiles like the M483A1. The M42 is smaller and optimized primarily for anti-personnel effects with a secondary anti-light armor capability (65mm penetration). The M46 is larger with a more powerful shaped charge designed specifically for anti-armor effects (150mm+ penetration). A typical M483A1 projectile contains 64 M42 and 24 M46 submunitions, providing combined effects against both personnel and armored vehicles in the target area.
Q: Why does DPICM have such high dud rates compared to manufacturer specifications? A: Several factors contribute to field dud rates exceeding specifications: soft or yielding impact surfaces (mud, sand, snow, vegetation) cushion impact and prevent fuze function; ribbon entanglement on vegetation or debris can affect bomblet orientation; environmental conditions (extreme temperatures, humidity) affect fuze components; manufacturing variations across large production lots; age-related degradation of stockpiled munitions; and low or incorrect ejection altitudes. The small size of submunitions also makes quality control more challenging than for larger unitary munitions. Field conditions are far more variable than test conditions.
Q: How are DPICM projectiles employed tactically? A: DPICM is typically employed as part of massed artillery fires rather than single-round missions. Fire direction centers calculate firing data to place projectile burst points at optimal altitude over the target, creating overlapping patterns of submunition coverage. Multiple batteries may fire simultaneously for time-on-target effect. Typical missions include: suppression of enemy artillery and air defense systems; engagement of troops in defensive positions; interdiction of movement along roads and chokepoints; and area denial. The large area coverage makes DPICM effective against dispersed targets that would require numerous unitary HE rounds to engage.
Q: Can M42 duds be safely identified and avoided? A: While M42 submunitions may be visible on the surface, safe identification and avoidance is extremely challenging for several reasons: bomblets may be partially buried or concealed in debris and vegetation; the nylon ribbon may be the only visible indicator, with the bomblet itself hidden; environmental changes (rainfall, vegetation growth) can obscure previously visible bomblets; multiple submunitions in an area make thorough visual search impractical; and any approach close enough for identification risks triggering a dud. Only systematic clearance by trained EOD personnel using appropriate detection and disposal methods can render an area safe.
Q: Why is pre-scored fragmentation used on the M42? A: Pre-scored fragmentation provides controlled breakup of the steel case upon detonation. Without scoring, the case might fragment into irregularly-sized pieces with unpredictable distribution. The machined grooves ensure the case breaks along predetermined lines, creating uniformly-sized fragments for consistent lethality. This controlled fragmentation optimizes anti-personnel effectiveness by producing fragments of sufficient size and velocity to cause casualties while maximizing the number of fragments (and thus hit probability) within the lethal radius.
Q: What happens when an M42 submunition strikes an armored vehicle? A: When functioning properly against an armored target, the M42’s effects occur in rapid sequence: the all-ways acting fuze initiates upon impact; the shaped charge jet forms and penetrates the armor (up to 65mm); jet penetration creates behind-armor effects including spall and possibly crew casualties; simultaneously, the fragmentation case detonates, producing high-velocity fragments; external fragmentation may damage exposed components, optics, antennas, and tracks. The M42’s 65mm penetration is insufficient against main battle tank armor but effective against the thinner armor of APCs, IFVs, trucks, and the top/rear aspects of some combat vehicles.
Q: How does artillery ammunition with M42 submunitions differ from regular HE rounds? A: Standard HE artillery rounds detonate on impact (or at preset height/time), creating a single blast and fragmentation effect. DPICM cargo rounds like the M483A1 are designed as delivery vehicles—the projectile case opens at altitude, ejecting submunitions that spread across the target area. This creates dozens of smaller explosions distributed across a much larger area rather than a single concentrated blast. DPICM is more effective against dispersed targets (troops spread out, vehicle convoys) while HE is more effective against point targets (bunkers, buildings, single vehicles).
Q: What clearance methods are used for M42 contaminated areas? A: Clearance of M42-contaminated areas requires systematic EOD operations: aerial and satellite imagery may indicate impact areas; ground survey establishes contamination boundaries; visual search identifies surface UXO (recognizing many bomblets may be concealed); metal detection helps locate buried bomblets; disposal is typically by demolition-in-place or remote destruction to avoid handling; mechanical clearance (flails, tillers) may be used in some scenarios to expose or detonate buried bomblets; and area must be resurveyed after clearance operations. Complete clearance is difficult due to partial burial and detection challenges, often requiring multiple clearance passes.
This document is for educational and training purposes only. All ordnance should be treated as dangerous until rendered safe by qualified EOD personnel. Never attempt to handle, move, or disturb any suspected explosive ordnance.