M819 81mm Bursting Smoke (Red Phosphorus) Mortar

1. Overview

The M819 is a United States 81mm bursting smoke mortar cartridge designed to produce rapid, dense screening smoke for tactical obscuration. Unlike white phosphorus (WP) smoke rounds that burn and disperse, the M819 uses red phosphorus (RP) as its smoke-producing agent, offering comparable screening effectiveness with reduced incendiary hazard and improved safety characteristics. This round provides infantry battalions with organic capability to obscure maneuver, mark positions, and screen breaching operations.

2. Country/Bloc of Origin

  • Country of Origin: United States of America
  • Development Period: 1980s-1990s, developed as a safer alternative to WP smoke rounds
  • Manufacturer: Produced by U.S. defense contractors under government contract
  • International Distribution: Exported to NATO allies and U.S. security partners
  • Current Status: In active service with U.S. Army and Marine Corps; standard 81mm smoke round

3. Ordnance Class

  • Type: Mortar cartridge (complete round)
  • Primary Role: Screening smoke, tactical obscuration, target marking
  • Delivery Method: Muzzle-loaded, drop-fired from M252 and other 81mm smoothbore infantry mortars
  • Category: Smoke/obscurant munition

4. Ordnance Family / Nomenclature

  • Official Designation: Cartridge, 81mm, Smoke, RP, M819
  • NSN: 1310-01-244-2010 (representative; may vary by lot)
  • DODIC: C636
  • Family Variants:
    • M819 – Standard production model
  • Related Smoke Rounds:
    • M375 series – WP (white phosphorus) smoke (older design)
    • M816 – Infrared/visible screening smoke
    • M853A1 – Illumination round (different role but same family)
  • Complementary Rounds:
    • Used in conjunction with M821/M889 HE for combined effects

5. Hazards

Primary Hazards

  • Toxic Smoke: Red phosphorus smoke is an irritant; inhalation hazards exist in confined spaces
  • Thermal Hazard: RP generates significant heat during combustion; fire hazard to dry vegetation and combustible materials
  • Bursting Charge: Contains small explosive charge for case rupture; blast hazard at close range
  • Phosphorus Burns: While less severe than WP, RP particles can cause burns if in direct contact with skin

Sensitivity Considerations

  • Fuze Sensitivity: Impact fuzes are sensitive when armed
  • Propellant Hazards: Increment charges flammable and potentially unstable if deteriorated
  • RP Stability: Red phosphorus more stable than white phosphorus but still reactive with moisture

UXO Considerations

  • Unexploded M819 rounds remain hazardous due to fuze and bursting charge
  • RP fill may degrade over time, potentially increasing reactivity
  • Damaged rounds may expose RP to air, causing spontaneous ignition
  • Do not approach, move, or disturb; treat as any other UXO

Special Precautions

  • Avoid breathing smoke produced by RP munitions
  • Do not use in enclosed spaces without respiratory protection
  • Coordinate smoke employment to avoid obscuring friendly positions

6. Key Identification Features

Physical Characteristics

  • Length: Approximately 460mm (18.1 inches) overall
  • Diameter: 81mm (3.19 inches) body
  • Weight: 3.75 kg (8.27 lbs) complete round
  • Body Shape: Similar to HE rounds; ogival nose with cylindrical body

Visual Identification

  • Body Color: Light green or light grey (smoke munition designation)
  • Markings:
    • Yellow band with “RP” markings indicating red phosphorus fill
    • Nomenclature stenciled: “CART 81MM SMOKE RP M819”
    • Lot number, year of manufacture, loading facility code
  • Fuze Well: Standard 81mm fuze threading
  • Tail Assembly: Standard 81mm tail boom and fin assembly

Distinguishing Features

  • Light green/grey body color immediately distinguishes from olive drab HE rounds
  • “RP” marking critical for identification (versus “WP” for white phosphorus)
  • Yellow band indicates presence of hazardous filler
  • Lighter weight than HE rounds due to RP fill versus explosive

Color Coding Reference (U.S. 81mm Mortar Rounds)

Body ColorTypeExample
Olive DrabHEM374A2, M821
Light Green/GreySmokeM819, M375
WhiteIlluminationM853A1
BluePracticeM880

7. Fuzing Mechanisms

Primary Fuze

  • M772 Point-Detonating Fuze (or equivalent)
  • Function: Impact (superquick) – detonates bursting charge on ground contact to disperse RP fill

Fuze Characteristics

  • Arming Method: Setback and spin-arm during launch
  • Arming Distance: 10-30 meters from muzzle
  • Function: Superquick only; no delay option
  • Safety Features: Standard bore-riding pin and setback safety mechanisms

Operational Sequence

  1. Round fired from mortar
  2. Fuze arms during flight (setback and spin)
  3. Upon ground impact, fuze initiates
  4. Small bursting charge ruptures case body
  5. Red phosphorus ejected and ignites upon air exposure
  6. RP burns, generating dense white smoke

Smoke Production

  • Duration: Smoke production lasts approximately 60-90 seconds per round
  • Coverage: Single round produces smoke cloud covering approximately 20-30 meter radius
  • Screening Effect: Effective in visual and near-infrared spectrum

8. History of Development and Use

Development Context

The M819 was developed in response to concerns about the severe burn hazards and toxicity associated with white phosphorus smoke munitions. White phosphorus, while highly effective as a smoke agent, poses significant risks to both friendly troops and civilians due to its extremely caustic burning characteristics. Red phosphorus was identified as an alternative that could produce comparable smoke effects with improved safety margins.

Design Philosophy

  • Reduced Incendiary Effect: RP burns at lower temperatures than WP
  • Improved Handling Safety: RP is more chemically stable during storage and handling
  • Environmental Considerations: RP produces less toxic combustion products
  • Maintained Effectiveness: Smoke screening performance comparable to WP rounds

Operational History

  • Introduction: Entered U.S. service in the late 1980s/early 1990s
  • Gulf War (1991): Limited use; HE and WP more commonly employed
  • Operations in Iraq/Afghanistan (2001-2021): Regularly used for tactical obscuration during offensive and defensive operations
  • Current Status: Standard 81mm smoke round in U.S. inventory

Tactical Employment

The M819 is used for:

  • Screening friendly movement from enemy observation
  • Obscuring enemy positions during assault
  • Marking targets for supporting fires or aircraft
  • Creating smoke lines to deceive enemy as to axis of advance
  • Supporting breaching operations and casualty evacuation

9. Technical Specifications

SpecificationValue
Caliber81mm
Overall Length~460mm (18.1 in)
Total Weight3.75 kg (8.27 lbs)
Body MaterialSteel
Smoke AgentRed Phosphorus (RP)
RP Fill Weight~500-600g
Bursting ChargeSmall explosive charge for case rupture
Muzzle Velocity100-250 m/s (varies with charge)
Maximum Range~5,500m (with M252)
Minimum Range~70m
Smoke Duration60-90 seconds
Smoke Coverage~20-30m radius per round
Number of Charges0-4 increments + primary cartridge
Operating Temperature-40°F to +125°F (-40°C to +52°C)

10. Frequently Asked Questions

Q: What is the difference between red phosphorus (RP) and white phosphorus (WP) smoke munitions? A: White phosphorus ignites spontaneously in air and burns at extremely high temperatures (~1,500°C), causing severe, deep burns that are difficult to extinguish. Red phosphorus is an allotrope of phosphorus that is more chemically stable; it burns at lower temperatures and produces similar screening smoke but with significantly reduced burn severity if personnel are exposed. RP munitions were developed specifically to reduce the casualty-producing effects on friendly troops and non-combatants while maintaining tactical smoke effectiveness.

Q: Is the smoke from M819 rounds safe to breathe? A: No smoke is completely safe to inhale. RP smoke is an irritant and can cause respiratory distress, particularly in high concentrations or enclosed spaces. Personnel should avoid prolonged exposure and use respiratory protection when operating in dense smoke. The smoke is designed for outdoor tactical use where it disperses rapidly. In confined spaces, smoke concentration can reach hazardous levels quickly.

Q: How many M819 rounds are typically needed to create an effective smoke screen? A: Effectiveness depends on wind conditions, terrain, and desired coverage area. As a general guideline: a company-sized element might employ 4-8 rounds to establish an initial screen, with additional rounds fired at 30-60 second intervals to maintain the screen during movement. Fire direction centers calculate smoke requirements based on wind speed, target dimensions, and duration needed.

Q: Can the M819 be used for marking targets? A: Yes, though it’s not the primary role. The distinctive white smoke can mark positions for supporting fires or aircraft. However, dedicated marking rounds (HC or colored smoke) are preferred when precise identification is required. The M819’s smoke can also mark target reference points during combined arms operations.

Q: What fire hazard does the M819 present? A: While significantly less incendiary than WP, the M819’s RP fill still generates substantial heat during combustion. It can ignite dry grass, leaves, and other combustible materials. This is an important consideration in arid environments or during drought conditions. Units should assess fire risk before employing smoke rounds and have contingencies for fire control.

Q: How do I distinguish the M819 from older WP smoke rounds in the field? A: Key identification: M819 will be marked “RP” while older rounds are marked “WP.” Both typically have light green or grey body color with yellow bands. The nomenclature stenciling (M819 vs M375 series) is definitive. When in doubt, treat all smoke munitions with caution—both RP and WP present burn and inhalation hazards. Check lot numbers and date stamps; RP rounds entered service in the late 1980s.

Q: What is the proper response if personnel are exposed to burning RP? A: Remove the individual from the smoke area immediately. Unlike WP, which requires water submersion or wet material to prevent re-ignition, RP burns can be treated more conventionally. Remove contaminated clothing, flush burned areas with water, and seek medical attention. Do not attempt to pick out embedded particles—this is a task for medical personnel. Monitor for respiratory symptoms from smoke inhalation.

Q: Can weather conditions affect M819 performance? A: Yes, significantly. Wind disperses smoke rapidly—in high winds, effective screening may require substantially more ammunition or may be impractical. Rain can suppress smoke production. Temperature inversions can keep smoke close to the ground longer, improving coverage but potentially increasing inhalation hazard to ground troops. Fog and high humidity can affect smoke visibility and dispersion. Fire direction centers factor weather conditions into smoke planning.

This material is for educational and training purposes only. All ordnance should be considered dangerous until rendered safe by qualified EOD personnel. Never handle suspected unexploded ordnance. Report all UXO finds to appropriate military or civilian authorities.