NATO 155mm M105 Bursting Smoke Projectile
Overview
The 155mm M105 Bursting Smoke Projectile is a standard NATO smoke round designed to provide rapid smoke screening through impact detonation and dispersal of white phosphorus (WP) or hexachloroethane (HC) smoke agent. Unlike base-ejection smoke projectiles that deploy canisters, the M105 is a bursting-type round that detonates on impact to fragment the projectile body and scatter smoke-producing material over the target area. The M105 provides immediate smoke generation and has secondary incendiary effects when filled with white phosphorus. This projectile has been a standard U.S. and NATO smoke round for decades, widely employed for screening, marking, and obscuration missions.
Country/Bloc of Origin
- Primary Origin: United States of America
- Development Period: 1950s-1960s
- Design Authority: U.S. Army
- Primary Manufacturers: Multiple U.S. ammunition production facilities
- NATO Adoption: Standardized across NATO member nations
- International Production: Licensed or procured by numerous allied nations
- Current Status: Remains in active inventory with U.S. military and NATO allies
- Export Status: Widely exported to U.S. allies and partners
Ordnance Class
- Type: Artillery projectile, smoke (bursting type)
- Primary Role: Tactical smoke screening, target marking, obscuration
- Secondary Role: Incendiary effect (WP fill)
- Delivery Method: Gun-launched from 155mm howitzers
- Category: Conventional ammunition, special purpose
- Smoke Generation Method: Bursting dispersal of smoke agent
- Fire Support Role: Rapid smoke screening, target marking for aviation, obscuring enemy observation, anti-materiel (WP)
Ordnance Family/Nomenclature
Primary Designation:
- U.S. Designation: M105
- Full Nomenclature: Cartridge, 155mm, Smoke, WP, M105 (or Cartridge, 155mm, Smoke, HC, M105)
- NATO Stock Number (NSN): Multiple NSNs based on fill type and propellant configuration
Designation Variants:
- M105: Standard bursting smoke (WP or HC fill)
- M105A1: Improved variant
- M105B1: Further improvements
Fill Type Variations:
- WP (White Phosphorus): Primary smoke/incendiary fill
- HC (Hexachloroethane): Alternative smoke fill, reduced incendiary effect
- RP (Red Phosphorus): Less common variant
Related Family Members:
- M825/M825A1: Improved WP smoke rounds
- M116: Base-ejection smoke (different design philosophy)
- M110: Older 155mm WP smoke round
Compatible Weapon Systems:
- M109 family self-propelled howitzer (all variants)
- M777 towed howitzer
- M198 towed howitzer
- M114 towed howitzer (historical)
- All NATO-standard 155mm systems
- Numerous export customer artillery systems
Propellant Configurations:
- M3A1 (white bag) propellant charge
- M4A2 (green bag) propellant charge
- M119 series modular propellant charges (modern systems)
Hazards
Primary Hazards:
White Phosphorus (WP) Fill Hazards:
- Incendiary Effect: WP burns at approximately 800°C (1,472°F)
- Spontaneous Ignition: WP ignites spontaneously in air
- Severe Burns: Contact with burning WP causes deep, difficult-to-treat chemical burns
- Re-ignition Risk: WP particles can re-ignite after apparent extinguishment when oxygen is reintroduced
- Toxic Smoke: WP smoke (phosphorus pentoxide) is highly irritating and toxic
- Fire Hazard: Can ignite vegetation, structures, and equipment
Blast and Fragmentation:
- Bursting Charge: Small explosive charge fragments projectile body
- Steel Fragments: Body fragmentation produces lethal shrapnel
- Fragment Radius: Lethal fragments possible within 50-100+ meters
- Blast Overpressure: Minimal compared to HE rounds
Smoke Inhalation:
- WP Smoke Toxicity: Phosphorus pentoxide causes severe respiratory irritation and chemical pneumonitis
- HC Smoke: Zinc chloride fumes cause respiratory irritation
- Confined Space Danger: Concentrated smoke in enclosed areas is extremely hazardous
UXO Hazards:
- Fuze Failure: Intact rounds contain bursting charge and full smoke agent
- Exposed WP: Damaged rounds may leak white phosphorus
- Spontaneous Ignition: WP UXO may self-ignite when disturbed
- Environmental Release: WP contaminates soil and water
- Delayed Ignition: Buried WP particles can ignite when excavated
Handling Hazards:
- Fuze Sensitivity: Point-detonating fuzes are impact-sensitive when armed
- WP Container Integrity: Any damage risks WP exposure and ignition
- Temperature Sensitivity: Extreme temperatures affect WP stability
Key Identification Features
Dimensions:
- Length (projectile): Approximately 605mm (23.8 inches)
- Diameter: 155mm (6.1 inches)
- Weight (complete round): Approximately 41-43 kg (90-95 lbs)
- Weight (projectile only): Approximately 35 kg (77 lbs)
Physical Characteristics:
- Nose: Ogival profile with point-detonating fuze well
- Body: Steel shell, thinner-walled than HE projectiles
- Base: Flat or slightly concave
- Rotating Band: Copper alloy, single band
- Fill Access: Base plug for smoke agent filling
Color Schemes (U.S./NATO Standard):
- Body Color: Light green
- Markings Color: Yellow (indicating smoke fill)
- WP Indicator: “WP” stenciled on body
- HC Indicator: “HC” stenciled on body
Marking System:
- Nomenclature: “M105” and full designation
- Fill Type: Clearly marked (WP, HC, or RP)
- Lot Number: Manufacturing batch
- Date: Manufacture date
- Weight Zone: Weight classification for fire control
- Ammunition Lot Number: Complete round identification
- Manufacturer Code: Production facility identifier
Distinctive Features:
- Point-detonating fuze (nose-mounted)
- Yellow smoke identification markings
- Lighter construction than comparable HE rounds
- Fill type clearly stenciled
- Single rotating band
Distinguishing from HE Projectiles:
- Yellow markings (smoke) vs. unmarked or yellow band (HE varies)
- “WP” or “HC” designation
- Different fuze settings/options
- Thinner body walls (lighter weight)
Fuzing Mechanisms
Standard Fuzes:
M557 Point-Detonating Fuze:
- Most common fuze for M105
- Super-quick function for immediate surface burst
- Delay option (0.05 seconds) for slight penetration
- Mechanical, impact-activated
M739 Point-Detonating Fuze:
- Alternative PD fuze
- Similar function to M557
M582 Multi-Option Fuze:
- Point-detonating with super-quick and delay
- Time function option
Fuze Configuration:
- Thread Pattern: Standard U.S./NATO artillery fuze thread
- Setting Requirement: None for standard super-quick function; delay requires fuze adjustment
Arming Sequence:
- Setback: Propellant ignition accelerates projectile; setback force releases primary safety
- Spin: Barrel rifling imparts rotation; centrifugal force acts on arming mechanism
- Muzzle Exit: Projectile leaves barrel; arming continues
- Arm Distance: Fuze fully arms after minimum safe distance (~50-100 meters from muzzle)
- Flight: Projectile travels to target area
- Impact: Nose contact activates firing pin
- Detonation: Firing pin strikes detonator, initiating booster and bursting charge
- Fragmentation: Projectile body ruptures, dispersing smoke agent
Bursting Charge:
- Small explosive charge (typically TNT or Composition B)
- Sufficient to rupture shell body and disperse contents
- Does not consume smoke agent; agent burns after dispersal
Safety Features:
- Bore-safe design
- Setback interlock
- Centrifugal (spin) arming requirement
- Minimum arming distance
History of Development and Use
Development Background: The M105 was developed in the post-World War II era as the U.S. Army standardized on 155mm as its primary medium artillery caliber. The requirement was for a bursting-type smoke projectile that could provide rapid smoke screening and target marking while maintaining compatibility across the growing family of 155mm howitzers.
Historical Timeline:
- 1950s: Development of M105 to replace older smoke ammunition
- 1960s: Standardization and widespread fielding
- Vietnam War: Extensive use for screening and marking; WP also used for anti-personnel effect
- 1970s-1980s: Continued NATO standardization and stockpiling
- 1991 Gulf War: Employed for smoke missions
- 2000s-Present: Continued use in Iraq and Afghanistan for smoke and illumination support
- Ongoing: Remains in active inventory; M825 series increasingly supplements for some missions
Combat Employment:
Vietnam War (1965-1973):
- Heavy use for marking targets for aircraft
- Screening fire for ground operations
- Anti-personnel and anti-materiel use of WP
- Extensive tactical employment
Middle East Conflicts:
- Used by multiple nations in Arab-Israeli conflicts
- Iraqi use during Iran-Iraq War
- Coalition employment in Gulf War
Global War on Terror:
- Smoke screening in urban operations
- Target marking for close air support
- Limited urban use due to incendiary concerns
Tactical Doctrine: The M105 is employed for:
- Immediate Screening: Rapid smoke generation on impact
- Target Marking: WP visible smoke and thermal signature for aircraft
- Obscuration: Blinding enemy observation posts
- Anti-Materiel: WP incendiary effect against flammable targets
White Phosphorus Controversy: The incendiary effects of WP smoke rounds have made their use controversial, particularly in populated areas. While legally classified as smoke/obscurant ammunition rather than incendiary weapons under international law when used for smoke purposes, the severe burns caused by WP have led to policy debates and restrictions on employment in some contexts.
Current Status:
- Remains in U.S. and NATO inventory
- Supplemented by M825 series for some applications
- Subject to national rules of engagement regarding WP employment
- Active production continues
Technical Specifications
| Specification | Value |
|---|---|
| Caliber | 155mm |
| Projectile Weight | ~35 kg (77 lbs) |
| Complete Round Weight | ~41-43 kg |
| Projectile Length | ~605mm (23.8 in) |
| Smoke Fill (WP) | ~6.8 kg (15 lbs) |
| Bursting Charge | ~0.5-0.8 kg TNT or Comp B |
| Muzzle Velocity | ~564-684 m/s (depending on charge) |
| Maximum Range (M109A6) | ~18,000-22,000 m |
| Maximum Range (M777) | ~24,000+ m |
| Smoke Duration | 1-3 minutes (terrain/weather dependent) |
| WP Burning Temperature | ~800°C (1,472°F) |
| Fuze Type | Point-detonating (PD) |
| Operating Temperature | -40°C to +63°C |
Smoke Coverage (Approximate):
| Condition | Coverage |
|---|---|
| Single Round | ~30-50m diameter smoke cloud |
| Wind Calm | Dense localized smoke |
| Light Wind | Drifting smoke screen |
| Effective Screening | Multiple rounds required |
Propellant Charge Ranges (M109A6):
| Charge | Approximate Range |
|---|---|
| Zone 3 (white bag) | ~6,000 m |
| Zone 5 (white bag) | ~10,000 m |
| Zone 7 (green bag) | ~14,000 m |
| Zone 8 (green bag) | ~18,000 m |
Frequently Asked Questions
Q: What is the difference between the M105 (bursting smoke) and the M116 (base-ejection smoke)? A: The M105 is a bursting-type projectile that detonates on impact, fragmenting the shell body and scattering white phosphorus or HC smoke agent. It provides immediate but relatively short-duration smoke. The M116 is a base-ejection type that uses a time fuze to expel intact smoke canisters while in flight; the canisters fall to earth and burn to produce sustained smoke. Base-ejection provides longer smoke duration; bursting provides faster initial smoke generation. The M105 also has significant incendiary effect when WP-filled.
Q: Why is white phosphorus controversial? A: White phosphorus causes severe chemical burns that are extremely difficult to treat. WP particles can embed in flesh and continue burning, and can re-ignite after apparent extinguishment. While legal under international law when used for smoke/obscuration or illumination purposes, the injury potential has made WP employment controversial, particularly in urban areas or where civilians may be affected. Some nations have restricted WP use or imposed strict rules of engagement.
Q: Is the M105 classified as a chemical weapon? A: No. Under the Chemical Weapons Convention, the M105 is classified as smoke/obscurant ammunition, not a chemical weapon, when used for its intended purpose of smoke screening, marking, or illumination. The smoke-producing effect is primary, and the incendiary effect is secondary. However, if deliberately used primarily for its incendiary effect against personnel, legal and ethical questions arise. Protocol III of the Convention on Certain Conventional Weapons addresses incendiary weapons, with specific restrictions on use in populated areas.
Q: How does WP smoke differ from HC smoke? A: White phosphorus smoke is produced by the oxidation of elemental phosphorus, creating phosphorus pentoxide particles that absorb moisture to form a dense white smoke (phosphoric acid mist). HC (hexachloroethane) smoke is produced by a chemical reaction between hexachloroethane and zinc oxide, producing zinc chloride smoke. WP smoke is highly toxic and caustic; HC smoke is irritating but less acutely dangerous. WP has significant incendiary effect; HC has minimal incendiary potential.
Q: What are the medical treatment considerations for WP injuries? A: WP burns require immediate irrigation with water or saline to prevent continued burning. WP particles must be kept wet to prevent re-ignition. Copper sulfate solution can be applied to help identify particles (turns black on contact) but should be followed by irrigation. Embedded particles require surgical removal. WP injuries are complicated by the chemical toxicity of phosphorus compounds absorbed through burned tissue, potentially causing systemic effects including liver and kidney damage. Specialized burn treatment facilities are required.
Q: How is the M105 employed tactically? A: The M105 is used for: (1) Screening Smoke – creating visual obscuration to mask friendly movement or positions; (2) Target Marking – WP produces distinctive white smoke and thermal signature visible to aircraft; (3) Blinding Smoke – placed on enemy positions to obscure their observation; (4) Anti-Materiel – WP incendiary effect can ignite flammable targets. Fire direction centers calculate fuze settings and fire missions based on desired coverage, wind conditions, and tactical requirements. Multiple rounds are typically fired to create effective screens.
Q: What happens if an M105 fails to detonate? A: An M105 dud creates a serious UXO hazard. The intact projectile contains approximately 6.8 kg of white phosphorus and a functioning fuze that may be armed. Impact damage may compromise the shell body, potentially exposing WP. Disturbing the round could cause fuze functioning or WP ignition. WP UXO is particularly dangerous because the phosphorus can spontaneously ignite when exposed to air. All suspected UXO must be reported to EOD authorities; do not approach, touch, or attempt to move.
Q: How does the M825 series relate to the M105? A: The M825/M825A1 is a newer WP smoke projectile that uses felt wedges saturated with WP rather than bulk liquid WP fill. When the projectile bursts, the felt wedges scatter and burn, producing smoke with somewhat less intense incendiary effect compared to scattered liquid WP. The M825 series was developed to provide smoke capability with reduced collateral incendiary effect while maintaining effective obscuration.
SAFETY NOTICE: This lesson is intended for educational and training purposes. All ordnance should be considered dangerous until proven safe by qualified personnel. Unexploded ordnance should never be handled by untrained individuals—report findings to military or law enforcement authorities.