US M722A1 60mm Bursting Smoke

1. Overview

The M722A1 is a United States 60mm white phosphorus (WP) smoke mortar cartridge, representing an improved version of the M722 designed for the M224 Lightweight Company Mortar System (LWCMS). This bursting smoke round incorporates enhanced insensitive munitions characteristics while maintaining the screening, signaling, target marking, and secondary incendiary capabilities of its predecessor. The A1 suffix indicates improvements in safety and insensitive munitions compliance, making the round more resistant to unintended ignition from fire, impact, or other stimuli while maintaining tactical effectiveness.

2. Country/Bloc of Origin

  • Country: United States of America
  • Development Period: Late 1990s–early 2000s
  • Background: Developed as part of the broader US military effort to field insensitive munitions (IM) compliant ammunition
  • Manufacturers: US Army ammunition plants and contractors
  • Service Entry: Early 2000s

3. Ordnance Class

  • Type: Mortar Cartridge, Smoke (White Phosphorus)
  • Insensitive Munitions Compliance: Enhanced IM characteristics
  • 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, M722A1
  • Predecessor: M722 60mm WP Smoke
  • Related Rounds:
    • M722: Original WP smoke cartridge
    • M302A1/M302A2: Legacy 60mm WP smoke for M2/M19 mortars
  • Family Relationship:
    • Ballistically matched to M720A1 HE and M721 Illumination
    • Part of M224 LWCMS standard ammunition suite
  • Compatible Weapon Systems:
    • M224 60mm Lightweight Company Mortar System
    • M224A1 60mm Mortar
    • M19 60mm Mortar (at reduced charges)

5. Hazards

Primary Hazards

  • White Phosphorus Burns: WP ignites spontaneously in air, burning at approximately 800°C (1,472°F); contact causes severe chemical burns
  • Toxic Smoke: WP combustion products are toxic if inhaled
  • Incendiary Effect: Scattered WP particles ignite combustible materials
  • Fragmentation: Bursting body produces fragmentation hazard

Insensitive Munitions Characteristics

The M722A1 incorporates design features to reduce unintended ignition:

  • Bullet Impact: Improved resistance to ignition from small arms fire
  • Fragment Impact: Reduced sensitivity to fragment impact
  • Fire Exposure: Enhanced resistance to cook-off in fire
  • Sympathetic Detonation: Reduced risk of chain reaction in stored ammunition

Important: IM compliance reduces accidental ignition risk but does not eliminate hazards of the WP filler. All handling, storage, and UXO considerations remain critical.

Sensitivity Considerations

  • Impact Function: Point-detonating/delay fuze functions on impact or with delay
  • WP Hazard: White phosphorus remains pyrophoric and toxic regardless of IM improvements
  • Fuze Status: Armed fuzes in UXO condition present impact sensitivity

UXO Considerations

  • Enhanced Stability: IM features may increase likelihood of intact UXO (round survives impact without detonation)
  • WP Exposure: Any body damage may expose WP to air, causing ignition
  • Fuze State: Unexploded rounds may have armed fuzes sensitive to disturbance
  • Environmental Hazard: WP contamination persists in soil and water

Special Hazards

  • WP particles continue burning as long as oxygen is available
  • Reignition occurs when extinguished WP is re-exposed to air
  • Embedded WP particles continue burning inside wounds
  • WP burns require specialized medical treatment

6. Key Identification Features

Dimensions

  • Caliber: 60mm
  • Overall Length: Consistent with M720A1/M721 series
  • Body Diameter: 60mm nominal
  • Complete Round Weight: Similar to M722

Physical Characteristics

  • Body Construction: Thin-wall steel body optimized for WP dispersion with IM-enhanced design
  • Payload: Bulk white phosphorus with integral burster charge
  • Fin Assembly: Six-blade fin assembly with obturating ring
  • Fuze: Point-detonating/delay 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 M722A1 SMK WP” (designation)
    • “WP” indication
    • Lot number and date
    • Manufacturer code
    • May include IM compliance markings

Distinctive Features

  • Light Green/Gray Color: Distinguishes from OD green HE rounds
  • Yellow Band: Indicates WP content (special hazard)
  • “A1” Designation: Indicates improved IM-compliant variant
  • Modern Manufacture Date: Production dating from early 2000s onward

7. Fuzing Mechanisms

Primary Fuze: Point-Detonating/Delay Fuze

The M722A1 uses a point-detonating fuze with delay capability.

Fuze Components

  • Striker Assembly: Inertia-driven firing mechanism
  • Detonator: Primary explosive charge
  • Booster: Initiates burster charge
  • Delay Element: Optional function for penetration before burst
  • Arming Mechanism: Setback and/or spin-actuated safety

Function Modes

  • Impact: Functions on ground contact (primary mode)
  • Delay: Functions after brief penetration delay

Function Sequence

  1. Pre-Launch: Fuze unarmed with safety mechanisms engaged
  2. Launch: Propellant ignition creates setback force, initiating arming sequence
  3. Flight: Fuze completes arming during trajectory
  4. Impact: Striker initiates detonator
  5. Burst: Burster charge ruptures thin-wall body
  6. Dispersion: WP particles scatter and spontaneously ignite
  7. Smoke Generation: Burning WP produces dense white smoke

8. History of Development and Use

Development Background

The M722A1 was developed as part of the US Department of Defense’s Insensitive Munitions program. Following incidents where ammunition was accidentally ignited by fires, impacts, or other unplanned stimuli, the military prioritized development of ammunition with improved resistance to accidental ignition.

Insensitive Munitions Program

The IM program established requirements for ammunition to resist:

  • Bullet Impact: Single bullet strikes should not cause detonation
  • Fragment Impact: Fragments from nearby explosions should not cause sympathetic detonation
  • Slow Cookoff: Gradual heating (as in fire) should result in burning rather than detonation
  • Fast Cookoff: Rapid heating should result in minimal reaction
  • Sympathetic Reaction: Detonation of adjacent rounds should not cause chain reaction

Key Improvements Over M722

  • Enhanced body and filler design for IM compliance
  • Improved fuze safety mechanisms
  • Modified burster charge characteristics
  • Maintained tactical performance and ballistic match

Tactical Employment

The M722A1 supports identical tactical roles as the M722:

Screening Operations

  • Obscuring friendly movement
  • Blinding enemy observation
  • Supporting withdrawal and evacuation

Target Marking

  • Marking targets for close air support
  • Indicating objectives for follow-on forces
  • Confirming target location for fire support

Signaling

  • Visual communication between units
  • Position marking
  • Emergency signaling

Combat Use

  • Afghanistan (2001–2021): Screening and marking operations
  • Iraq (2003–2011): Urban and rural operations
  • Global War on Terror: Continuing service use

Current Status

  • In active production and service
  • Preferred WP smoke round for US forces due to IM compliance
  • Included in M224/M224A1 ammunition suite
  • Available for foreign military sales

9. Technical Specifications

SpecificationValue
Caliber60mm
Overall LengthSimilar to M720A1 series
Body Diameter60mm
Complete Round WeightSimilar to M722
FillerWhite Phosphorus (bulk)
Burster ChargeIntegral (IM-enhanced design)
FuzePoint-Detonating/Delay
PropellantM204 (4 increments)
Ignition CartridgeStandard 60mm type
Maximum Range3,200–3,800 m
Insensitive MunitionsEnhanced IM characteristics
Rate of Fire (Max)30 rounds/min
Rate of Fire (Sustained)15 rounds/min

10. Frequently Asked Questions

Q: What is the difference between the M722 and M722A1? A: The M722A1 incorporates insensitive munitions (IM) design features that reduce the likelihood of unintended ignition from fire, bullet impact, fragment impact, or sympathetic detonation. The tactical performance, ballistic characteristics, and smoke-generation capability remain essentially identical. The A1 variant is preferred due to improved safety during handling, transport, and storage.

Q: Does the IM compliance make the M722A1 safer as UXO? A: The IM features are designed to prevent accidental ignition during normal handling and storage—they do not make UXO safer to approach or handle. In fact, IM features may increase the likelihood that a malfunctioning round survives impact intact, potentially creating more UXO. The white phosphorus filler remains pyrophoric and toxic, and the fuze may be armed and sensitive. All UXO procedures apply fully.

Q: Why does WP continue to be used when it causes such severe injuries? A: White phosphorus remains in use because it provides rapid, reliable smoke generation that has not been fully matched by alternative technologies. The immediate ignition and dense smoke production make WP effective for emergency obscuration. Alternative smoke compositions generally require longer development time or have other operational limitations. However, the humanitarian concerns have driven research into WP alternatives.

Q: Can the M722A1 be mixed with M722 in combat loads? A: Yes, the M722A1 is ballistically identical to the M722 and can be used interchangeably in tactical employment. However, logistics and safety procedures should account for any mixing of IM and non-IM ammunition to ensure proper handling protocols are followed for each type.

Q: What is the proper response to WP contamination? A: For personnel exposed to WP:

  1. Remove contaminated clothing
  2. Immerse affected areas in water to prevent WP ignition
  3. Remove visible WP particles (under water if possible)
  4. Keep wounds wet during evacuation
  5. Seek immediate medical attention—surgical removal of embedded particles is required

For environmental contamination, evacuate the area and contact hazardous materials response teams.

Q: How does the M722A1 perform compared to other NATO 60mm smoke rounds? A: The M722A1 is among the most capable 60mm smoke rounds in NATO service, offering full-range ballistic match with M720A1 HE rounds, IM compliance, and reliable WP smoke generation. Its performance is comparable to or exceeds similar rounds used by NATO allies.

Q: Are there restrictions on using WP rounds? A: While WP is not banned under international law, its use is restricted. Protocol III of the Convention on Certain Conventional Weapons limits the use of incendiary weapons against personnel and in civilian areas. US doctrine emphasizes the legitimate screening and marking roles of WP munitions while acknowledging restrictions on anti-personnel employment.

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

Insensitive munitions features do not make UXO safe to approach

WP burns require specialized medical treatment

Establish a safe perimeter and mark the location

Report findings to military or law enforcement authorities immediately