155mm VX Chemical Projectile

1. Overview

The 155mm VX Chemical Projectile is a 155mm artillery round filled with VX nerve agent, one of the most lethal chemical warfare agents ever developed. VX is a persistent organophosphate nerve agent that disrupts the nervous system by inhibiting the enzyme acetylcholinesterase, leading to uncontrolled nerve impulse transmission, muscular paralysis, and death. The 155mm delivery platform was adopted by several nations—most notably the United States and Iraq—as a means of delivering VX over artillery ranges. While the U.S. has destroyed its VX stockpiles under the Chemical Weapons Convention, VX-filled munitions remain a critical concern in Middle Eastern conflict zones where legacy Iraqi stockpiles and undeclared caches may still exist. A single drop of VX absorbed through the skin can be lethal, making these munitions among the most hazardous items encountered in ordnance disposal.

2. Country/Bloc of Origin

Developer of VX Agent: United Kingdom (first synthesized at Porton Down in 1952); subsequently weaponized by the United States beginning in the late 1950s
U.S. Production: The U.S. Army produced VX in large quantities at the Newport Chemical Depot in Indiana from 1961–1968, filling various munitions including 155mm projectiles at Pine Bluff Arsenal and other facilities
Iraqi Production: Iraq produced VX at the Al Muthanna State Establishment during the late 1980s, though Iraqi VX production was less refined and quantities were smaller than the mustard and G-agent programs
Soviet/Russian Equivalent: The Soviet Union developed VX (Russian VX / VR / R-33), a structural isomer with similar properties, and filled it into various munitions
Period of Production: 1960s–1990s (U.S.); late 1980s–1991 (Iraq)
Other Nations: Several nations are suspected to have produced or stockpiled VX, including Syria and North Korea

3. Ordnance Class

Type: Chemical warfare artillery projectile
Primary Role: Persistent nerve agent contamination for area denial, casualty production, and terrain denial
Chemical Agent: VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) — a V-series persistent nerve agent
Delivery Method: Fired from 155mm howitzers
Category: Chemical munition; classified as a Schedule 1 chemical weapon under the Chemical Weapons Convention (CWC)

4. Ordnance Family / Nomenclature

U.S. Designations:
- M121/M121A1 – U.S. 155mm VX projectile (based on the M110/M116 HE projectile body)
- Filled at various U.S. Army chemical depots
Iraqi Designations: Iraqi VX-filled munitions were produced in limited quantities and were not systematically designated in open-source documentation; they followed similar patterns to other Iraqi chemical projectiles
Common Names: “VX round,” “nerve agent round,” “V-agent projectile,” “persistent nerve round”
Related Variants:
- M121 – Early U.S. 155mm VX projectile
- M121A1 – Improved variant
- M55 rocket – 115mm rocket with VX or GB fill (related U.S. chemical munition)
- 155mm Sarin (GB) projectiles – Non-persistent nerve agent variant
- 155mm mustard (HD) projectiles – Persistent vesicant variant
CWC Classification: Schedule 1 chemical weapon; production, stockpiling, and use strictly prohibited

5. Hazards

Primary Hazards:
- Extreme Lethality: VX is the most potent nerve agent in standard military inventories. The lethal dermal dose (LD50) is approximately 10 mg for a 70 kg adult—a quantity smaller than a single drop
- Persistent Agent: VX has extremely low volatility, meaning it does not evaporate quickly. It can persist on surfaces, equipment, and terrain for days to weeks under normal conditions, and months in cold weather or sheltered environments
- Multiple Exposure Routes:
  - Skin absorption (primary): VX is most dangerous as a contact hazard; it readily penetrates skin
  - Inhalation: While less volatile than G-agents, VX vapor or aerosol is lethal at very low concentrations
  - Ingestion: Contamination of food or water sources
  - Eye contact: Extremely rapid absorption through mucous membranes
- Mechanism of Action: VX irreversibly inhibits acetylcholinesterase, causing accumulation of acetylcholine at nerve junctions, leading to: miosis (pinpoint pupils), excessive secretions, bronchospasm, muscular twitching, seizures, respiratory failure, and death
Explosive Hazard: The projectile contains a burster charge to rupture the casing and disperse the agent; this explosive remains dangerous independently
Sensitivity Considerations:
- Standard fuze arming applies; the fuze is armed by firing forces
- Leaking VX from corroded casings creates an extreme contact hazard
- VX is an oily liquid that clings to surfaces and is difficult to decontaminate
- Cross-contamination risk is extremely high—trace amounts on gloves, tools, or equipment can transfer to personnel
Environmental Hazards:
- VX contaminates soil, water, vegetation, and structures
- Agent breakdown in the environment produces toxic degradation products
- Cold conditions dramatically extend persistence
UXO Considerations:
- Chemical UXO containing VX represents the highest hazard category in ordnance disposal
- Even heavily corroded projectiles may contain viable VX agent internally
- Any liquid residue on or around a suspect projectile must be assumed to be nerve agent until proven otherwise
- Mandatory full chemical protective equipment with highest-level nerve agent protection

6. Key Identification Features

Dimensions: Standard 155mm projectile dimensions—approximately 155mm (6.1 in) diameter, 600–700mm (23.6–27.6 in) overall length
Weight: Approximately 42–47 kg (92–104 lbs) complete
Shape: Standard 155mm ogival projectile body; externally similar to conventional HE and other chemical-filled rounds
Color and Markings:
- U.S. Convention:
  - Grey projectile body with green band(s) indicating chemical agent fill
  - Three green bands historically indicated VX (persistent nerve agent)
  - Stenciled nomenclature: “M121” or “M121A1” with agent symbol “VX,” lot number, and fill date
  - The marking “GAS” or the chemical hazard symbol may be present
- Iraqi Convention:
  - Marking conventions were less standardized; colored bands and Arabic stenciling indicated chemical fill
  - Iraqi VX munitions may not be readily distinguishable from other chemical fills without detection equipment
- WARNING: Paint and markings degrade over time; never rely solely on markings to determine chemical fill in aged or buried munitions
Distinctive External Features:
- Fill plug/pour hole on the projectile body—an indicator of liquid chemical fill (absent on standard HE)
- Oily residue, discolored soil, or dead vegetation near the item may indicate agent leakage
- VX in liquid form is an amber-to-brown oily liquid with very low odor (sometimes described as faintly sulfurous)
Material: Steel projectile casing

7. Fuzing Mechanisms

Type: Standard 155mm artillery fuzes; typically point-detonating (PD) fuzes for chemical projectiles
Common Fuzes Used:
- U.S. M557 (PD) or M572 (PD with delay) for the M121 series
- Iraqi chemical projectiles used various compatible PD fuzes
Functioning:
- On impact, the PD fuze initiates the central burster tube, which ruptures the projectile casing and disperses VX agent as liquid droplets over the target area
- The burster is designed to maximize agent dispersal rather than blast effect
- VX settles as a fine liquid film on surfaces, personnel, equipment, and vegetation
Arming: Standard setback and spin arming
Agent Dispersal Pattern: VX is dispersed as relatively large droplets compared to volatile agents, creating a localized but extremely persistent contamination zone
UXO Note: In dud projectiles, the burster charge remains intact, the fuze may be partially armed, and the full VX fill remains sealed (or leaking) inside the casing

8. History of Development and Use

VX was first synthesized in 1952 by British chemist Ranajit Ghosh at the Porton Down research facility while researching organophosphate pesticides. Its extraordinary toxicity was quickly recognized, and the formulation was shared with the United States under a bilateral defense agreement. The U.S. began large-scale VX production at the Newport Chemical Depot in 1961, producing approximately 4,400 tons of VX agent before production ceased in 1968.

U.S. 155mm VX Projectiles: The M121 series 155mm projectile was a primary VX delivery system in the U.S. chemical arsenal during the Cold War. Stockpiles were maintained at several depots across the continental United States and at forward-deployed locations in Europe and the Pacific. These weapons were intended as a strategic deterrent and for use in the event of a large-scale conventional war, particularly in the European theater against massed Warsaw Pact armored formations, where VX’s persistence would deny terrain and force enemy forces to operate in chemical protective equipment.

Iraqi VX Program: Iraq’s VX production efforts in the late 1980s were less successful than their mustard and G-agent programs. Iraqi VX was reported to be of lower purity and stability. Following the 1991 Gulf War, UNSCOM inspectors documented Iraqi VX production and some filling into munitions, though the full extent of the program remained a subject of dispute. Iraq’s failure to fully account for its VX stockpile was a significant factor in the ongoing disputes about Iraqi WMD compliance.

U.S. Stockpile Destruction: Under the Chemical Weapons Convention (ratified by the U.S. in 1997), the U.S. undertook destruction of its entire VX stockpile. The final VX munitions were destroyed at the Blue Grass Chemical Agent-Destruction Pilot Plant in Kentucky, with the overall U.S. chemical weapons destruction program completed in 2023. Destruction methods included neutralization (hydrolysis) and incineration.

Ongoing Concerns: While declared stockpiles have been destroyed, concerns persist about undeclared or unaccounted-for VX munitions in the Middle East and other regions. The 2017 assassination of Kim Jong-nam using VX agent in Malaysia demonstrated that VX production capability persists outside CWC oversight. Legacy VX-filled munitions may still be encountered in conflict zones, particularly in Iraq.

Current Status: U.S. stockpiles fully destroyed as of 2023. Iraqi and other Middle Eastern stockpiles partially destroyed under international supervision; unaccounted-for items remain a concern. VX production capability believed to persist in North Korea and potentially other non-CWC-compliant states.

9. Technical Specifications

Specification	Detail
Caliber	155mm
U.S. Designation	M121 / M121A1
Overall Length	~600–700mm (23.6–27.6 in)
Weight (complete)	~42–47 kg (92–104 lbs)
Chemical Fill	VX nerve agent; approximately 5–6 kg (11–13 lbs) per projectile
Burster Charge	Central burster tube, typically TNT or tetrytol
Agent Persistence	Days to weeks on open ground; weeks to months in cold/sheltered conditions
LD50 (dermal)	~10 mg for a 70 kg adult
LCt50 (inhalation)	~30–50 mg·min/m³
Agent Physical State	Amber to brown oily liquid; low volatility; nearly odorless
Boiling Point	298°C (568°F) — extremely low vapor pressure at ambient temperatures
Decontamination	Requires alkaline hydrolysis solutions (e.g., DS2, dilute bleach, or reactive skin decontamination lotion)

10. Frequently Asked Questions

Q: Why is VX considered more dangerous than sarin (GB) or other nerve agents? A: VX is more dangerous for several reasons: it is approximately 10 times more toxic than sarin via skin absorption, it is far more persistent (remaining hazardous on surfaces for days to weeks vs. hours for sarin), and it is primarily a contact hazard rather than an inhalation hazard, meaning it can contaminate terrain, equipment, and personnel who physically contact contaminated surfaces. While sarin is more dangerous as an inhalation threat in the short term, VX’s persistence and contact toxicity make it a more enduring battlefield hazard.

Q: What are the immediate symptoms of VX exposure? A: Symptoms depend on the route of exposure. Dermal exposure may produce: localized sweating and muscular fasciculations at the contact site, followed by progressive systemic effects including miosis (pinpoint pupils), excessive salivation, nausea, vomiting, diarrhea, tightness in the chest, difficulty breathing, convulsions, and respiratory failure. Vapor/aerosol exposure produces more rapid onset, typically beginning with miosis and rhinorrhea (runny nose) within seconds to minutes, progressing rapidly to respiratory distress and collapse. Without treatment, lethal exposure can cause death within 15 minutes to several hours depending on dose and route.

Q: What is the difference between VX dispersal from a 155mm projectile and a VX spray tank? A: A 155mm projectile uses a burster charge to rupture the casing and create a localized pattern of VX droplets in the impact area, typically covering an area of several hundred square meters. An aerial spray tank releases VX as a fine aerosol from an aircraft, creating a much larger contamination swath potentially covering thousands of square meters. The spray method is generally more efficient for area coverage, while artillery delivery is tactically flexible and can deliver VX to specific point targets.

Q: What antidotes are available for VX exposure? A: The standard military antidote regimen includes atropine (to counteract muscarinic effects like excessive secretions and bronchoconstriction) and pralidoxime chloride (2-PAM Cl) (to reactivate acetylcholinesterase before the agent-enzyme bond “ages” and becomes permanent). These are typically carried in auto-injector kits (ATNAA / MARK I kits). Diazepam is administered to control seizures. Treatment must be initiated as quickly as possible—the “aging” half-time for VX is approximately 48 hours, meaning pralidoxime remains effective longer for VX than for some other nerve agents like soman (GD), where aging occurs within minutes.

Q: How does VX persistence affect military operations and clearance activities? A: VX’s persistence means that a contaminated area remains dangerous for extended periods, potentially denying terrain to friendly forces, complicating medical evacuation, and requiring extensive decontamination before an area is safe. For clearance operations, it means that even decades-old VX munitions—whether intact, leaking, or partially detonated—remain extremely hazardous. All soil, vegetation, equipment, and debris in the vicinity of VX contamination must be treated as potentially lethal until detection equipment confirms decontamination.

Q: Can VX be detected in the field without specialized laboratory equipment? A: Yes, several field detection methods exist: M8 and M9 detection paper changes color in contact with liquid nerve agents (V-agents produce a dark green/black reaction on M8 paper). Chemical Agent Monitors (CAM) and the Joint Chemical Agent Detector (JCAD) can detect VX vapor, though VX’s low volatility makes vapor detection more difficult than with volatile agents. M256 detector kits provide presumptive identification through wet chemistry tests. However, definitive confirmation of VX typically requires laboratory analysis (GC-MS or LC-MS). The difficulty of detecting VX vapor in the field is one of the agent’s most dangerous characteristics.

Q: What protective equipment is required when approaching a suspected VX munition? A: Maximum chemical protection is mandatory: MOPP Level 4 or equivalent (JSLIST overgarment, protective mask with appropriate filters, chemical-resistant butyl rubber gloves and inner cotton gloves, and chemical-resistant overboots). Because VX is primarily a contact hazard, particular attention must be paid to glove integrity and boot protection. Any breach in the protective ensemble can be fatal. Detection equipment should be operational before approach, and a contamination control area must be established with a decontamination station.

Q: How does a 155mm VX projectile differ externally from a 155mm HE projectile? A: Externally, the projectile bodies are often identical or very similar in shape and size, as chemical projectiles frequently use the same body as HE rounds. The key differences are: chemical rounds bear colored bands and agent markings (green bands for nerve agent in U.S. convention), they typically have a fill plug for liquid agent filling, and the explosive content is limited to a central burster tube rather than a full explosive fill. In the field, particularly with aged or degraded munitions, these differences may be subtle, making chemical detection equipment essential for identification.

⚠️ SAFETY WARNING: VX nerve agent is among the most lethal substances known. All ordnance and ordnance components should be considered dangerous until rendered safe by qualified EOD personnel with specialized chemical weapons training. Chemical munitions require the highest level of protective equipment and specialized detection, handling, and destruction procedures. Never handle, move, or approach any suspected chemical munition without proper authorization, equipment, and training. Report all suspected chemical ordnance to appropriate military or law enforcement authorities immediately. This material is for professional educational and identification training purposes only.