US M722 60mm Bursting Smoke

1. Overview

The M722 is a United States 60mm white phosphorus (WP) smoke mortar cartridge designed for the M224 Lightweight Company Mortar System (LWCMS). This bursting smoke round provides rapid obscuration for screening and signaling, target marking for coordination with supporting arms, and secondary incendiary effects. The M722 functions by detonating on impact, dispersing white phosphorus particles that spontaneously ignite on contact with air, producing a dense white smoke cloud.

2. Country/Bloc of Origin

Country: United States of America
Development Period: Late 1980s–early 1990s
Type Classification Date: September 1991
Manufacturers: US Army ammunition plants and contractors
Service Entry: Early 1990s with expanded M224 ammunition family

3. Ordnance Class

Type: Mortar Cartridge, Smoke (White Phosphorus)
Primary Roles:
- Screening/obscuration
- Target marking
- Signaling
Secondary Role: Incendiary effects
Delivery Method: Muzzle-loaded, fin-stabilized mortar projectile with bursting WP fill

4. Ordnance Family / Nomenclature

Official Designation: Cartridge, 60mm, Smoke, WP, M722
Related Variants:
- M722A1: Improved WP smoke round with enhanced insensitive munitions characteristics
- M302/M302A1/M302A2: Legacy 60mm WP smoke cartridges for M2/M19 mortars
Compatible Weapon Systems:
- M224 60mm Lightweight Company Mortar System (primary)
- M224A1 60mm Mortar
- M19 60mm Mortar (at reduced charges)
Unit Cost: Approximately $329 (FY2002)

5. Hazards

Primary Hazards

White Phosphorus Burns: WP ignites spontaneously in air and burns at approximately 800°C (1,472°F); contact causes severe, deep chemical burns
Toxic Smoke: WP smoke is toxic if inhaled in concentration
Incendiary Effect: Scattered WP particles can ignite combustible materials
Fragmentation: Thin-wall bursting projectile produces some fragmentation hazard

Sensitivity Considerations

Impact Sensitivity: The M745 point-detonating fuze functions on impact
WP Hazard: White phosphorus is toxic and pyrophoric; it ignites spontaneously when exposed to air
Water Reaction: WP may react with water to produce phosphine gas (toxic)

UXO Considerations

Intact Rounds: Unexploded WP rounds contain hazardous pyrophoric material
Fuze Sensitivity: PD fuzes may be armed and sensitive in UXO condition
WP Exposure: Any damage to projectile body may expose WP to air, causing ignition
Environmental Hazard: WP contamination of soil and water presents long-term hazard

Special Hazards

Continued Burning: WP continues to burn as long as oxygen is available; fragments in wounds continue burning inside the body
Reignition: WP particles that are temporarily extinguished (e.g., by water submersion) will reignite when re-exposed to air
Medical Complications: WP burns require specialized treatment; embedded particles must be surgically removed under water

6. Key Identification Features

Dimensions

Caliber: 60mm
Overall Length: Similar to M720 HE (designed for ballistic compatibility)
Body Diameter: 60mm nominal
Complete Round Weight: Similar to M720 series

Physical Characteristics

Body Construction: Thin-wall steel body designed to burst and disperse WP
Payload: Bulk white phosphorus with integral burster charge
Fin Assembly: Six-blade fin assembly with four propellant increments
Fuze: M745 point-detonating fuze

Color and Markings

Body Color: Light green or light gray (smoke/WP color code)
Marking Color: Yellow band indicating hazardous filler
Typical Markings:
- “60MM M722 SMK WP” (designation)
- “WP” or white phosphorus indication
- Lot number and date
- Manufacturer code

Distinctive Features

Light Green/Gray Color: Distinguishes from OD green HE rounds
Yellow Band: Indicates special hazard (WP) content
M745 PD Fuze: Point-detonating fuze with protective cap
Thin-Wall Construction: Body designed for optimal WP dispersion

7. Fuzing Mechanisms

Primary Fuze: M745 Point-Detonating Fuze

The M745 is a point-detonating impact fuze designed for smoke and similar cartridges.

Fuze Components

Striker: Inertia-driven firing pin
Detonator: Primary explosive charge
Booster: Initiates burster charge
Arming Mechanism: Setback-actuated safety

Function Sequence

Pre-Launch: Fuze unarmed with striker restrained
Launch: Propellant ignition creates setback force, releasing primary safety
Flight: Fuze arms during trajectory
Impact: Striker drives forward into detonator
Detonation: Burster charge ruptures thin-wall body
Dispersion: WP particles scatter and ignite in air
Smoke Generation: Burning WP produces dense white smoke cloud

Fuze Function Mode

Impact: Functions on ground contact (primary mode)
The M745 is a relatively simple PD fuze optimized for WP dispersion

8. History of Development and Use

Development Background

The M722 was developed to provide the M224 LWCMS with a dedicated smoke round matching the ballistic performance of the M720 HE and M721 illumination cartridges. Legacy M302-series WP smoke rounds for the M2/M19 mortars had insufficient range for the M224’s extended engagement envelope.

Design Requirements

Ballistic Match: Trajectory compatible with M720/M721 for seamless mixed-round fire missions
Rapid Obscuration: Quick smoke development for screening
Marking Capability: Visible smoke signature for target marking

Type Classification

September 1991: M722 type classified and approved for production

Tactical Employment

The M722 supports multiple tactical applications:

Screening Operations

Obscuring friendly movement from enemy observation
Blinding enemy positions during maneuver
Creating smoke screens for withdrawal or evacuation

Target Marking

Marking targets for close air support (CAS)
Indicating objectives for follow-on forces
Confirming target location for fire support coordination

Signaling

Visual signals between units
Marking positions for coordination
Emergency signaling

Incendiary Effects

Starting fires in enemy positions
Destroying material and supplies
Creating additional obscuration through secondary fires

Combat Employment

Desert Storm (1991): Initial combat use
Afghanistan (2001–2021): Screening and marking missions
Iraq (2003–2011): Urban and rural operations
Continuous use in training and exercises

Controversy

White phosphorus weapons have generated controversy due to the severe injuries they cause. While legal for screening and obscuration purposes, their use against personnel is restricted under certain international conventions. The incendiary effects of WP cause particularly devastating burns that are difficult to treat.

9. Technical Specifications

Specification	Value
Caliber	60mm
Overall Length	Similar to M720 series
Body Diameter	60mm
Complete Round Weight	Similar to M720 series
Filler	White Phosphorus (bulk)
Burster Charge	Integral
Fuze	Point-Detonating, M745
Propellant	M204 (4 increments)
Ignition Cartridge	Standard 60mm ignition cartridge
Maximum Range	3,200–3,800 m (matches M720/M721)
Rate of Fire (Max)	30 rounds/min
Rate of Fire (Sustained)	15 rounds/min
Unit Cost	~$329 (FY2002)

10. Frequently Asked Questions

Q: What is white phosphorus and why is it used in smoke rounds? A: White phosphorus (WP) is a pyrophoric chemical element that ignites spontaneously when exposed to air. When a WP smoke round detonates, it scatters WP particles that immediately ignite, burning intensely and producing dense white smoke composed primarily of phosphorus pentoxide. This smoke develops rapidly and provides effective obscuration. WP has been used in smoke munitions since World War I due to its reliability and rapid smoke generation.

Q: Is the M722 a chemical weapon? A: No, the M722 is classified as an incendiary/smoke munition, not a chemical weapon. While WP smoke is toxic if inhaled in concentration, the primary purpose of the M722 is obscuration and marking rather than toxic effect. However, the use of incendiary weapons including WP against personnel is restricted under Protocol III of the Convention on Certain Conventional Weapons (CCW).

Q: What are the differences between the M722 and the legacy M302 WP rounds? A: The M722 is specifically designed for the M224 mortar with ballistic performance matching the M720/M721 family. It achieves greater range (3,200–3,800m vs. ~2,000m for M302 series) and is optimized for the M224’s longer barrel. The M302 series remains compatible with the M224 as Standard B ammunition but at reduced range.

Q: How should WP burns be treated? A: WP burns require specialized medical treatment. Initial care involves removing visible WP particles (preferably under water to prevent reignition), keeping affected areas wet to prevent particle reignition, and evacuating the casualty to medical facilities capable of surgical debridement. WP particles embedded in tissue will continue burning and must be removed surgically. The burns are complicated by chemical toxicity as well as thermal damage.

Q: What are the UXO hazards specific to WP rounds? A: WP UXO presents extreme hazards: (1) The fuze may be armed and impact-sensitive; (2) Any damage to the thin-wall body may expose WP, which will spontaneously ignite on air contact; (3) WP is toxic if inhaled or ingested; (4) WP can contaminate soil and groundwater. Never attempt to handle or move WP UXO; evacuate the area and report to EOD authorities.

Q: Can the M722 be used for casualty production? A: While WP rounds will cause severe casualties if used against personnel, their primary intended purpose is screening/obscuration and target marking. The use of incendiary weapons against personnel is restricted under international law, and US doctrine emphasizes the screening and marking roles. The casualty-producing capability exists but is considered a secondary effect.

Q: Why do WP burns continue after initial exposure? A: White phosphorus particles continue to burn as long as they have access to oxygen. Particles that embed in tissue continue burning inside the wound. Even if temporarily extinguished by water submersion, WP particles will reignite when re-exposed to air. This property makes WP burns particularly severe and difficult to treat compared to thermal burns from other sources.

Safety Notice

⚠️ All ordnance should be considered dangerous until verified safe by qualified EOD personnel.

This information is for educational and identification purposes only

Never handle, move, or disturb suspected WP ordnance

White phosphorus is pyrophoric (spontaneously ignites in air) and toxic

Damaged WP rounds may ignite without warning

WP burns require specialized medical treatment

Establish a safe perimeter and mark the location

Report findings to military or law enforcement authorities immediately