US 105mm M60 GB Chemical Projectile
Overview
The 105mm M60 GB Chemical Projectile is a chemical artillery round developed during the Cold War to deliver the nerve agent GB (Sarin) against enemy forces. Classified as a non-persistent chemical weapon, the M60 GB was designed to create a rapid-onset lethal vapor hazard that would dissipate relatively quickly, theoretically allowing friendly forces to occupy contaminated terrain shortly after attack. The round represents the U.S. Army’s effort to provide divisional artillery with an organic chemical capability during an era when chemical warfare was considered a realistic battlefield possibility. Understanding the M60 GB is critical for EOD personnel, humanitarian demining organizations, and chemical weapons destruction specialists, as stockpiled rounds continue to require disposal and the potential for encountering legacy munitions in former storage or testing sites remains.
SAFETY WARNING: GB (Sarin) is an extremely toxic nerve agent. Any suspected chemical munition must be treated with extreme caution. DO NOT approach, handle, or disturb suspected chemical ordnance. Evacuate the area and contact qualified military chemical warfare/EOD specialists immediately.
Country/Bloc of Origin
- Country: United States of America
- Development Period: 1950s-1960s (Cold War era)
- Production Period: Primary production during the 1950s-1960s
- Service Status: Declared obsolete; subject to Chemical Weapons Convention destruction requirements
- Storage: Formerly stockpiled at multiple U.S. military installations; now largely destroyed or in destruction queue
Ordnance Class
- Type: Artillery projectile (chemical ammunition)
- Primary Role: Delivery of chemical warfare agent (nerve agent)
- Agent Type: GB (Sarin) – non-persistent nerve agent
- Delivery Method: Fired from 105mm howitzers (M101, M102 series)
- Category: Chemical weapon; prohibited under Chemical Weapons Convention (CWC)
Ordnance Family/Nomenclature
Official Designation
- M60 GB – 105mm chemical projectile filled with nerve agent GB (Sarin)
Related Variants (Same Projectile Body)
- M60 HD – Filled with blister agent HD (Mustard)
- M60 VX – Filled with nerve agent VX
- M60 (training) – Inert training variant
Agent Designation
- GB – U.S. military designation for Sarin (Isopropyl methylphosphonofluoridate)
- NATO Code: GB
- CAS Number: 107-44-8
Historical Context
The M60 series represented the chemical fill for the standard 105mm howitzer round configuration, with different fills (GB, HD, VX) providing different tactical effects while using common projectile components.
Chemical Weapons Convention Status
- Prohibited: Manufacturing, stockpiling, and use prohibited under CWC (entered into force 1997)
- Destruction Required: All signatory nations required to destroy chemical weapons stockpiles
- U.S. Status: Active destruction program has eliminated majority of stockpile
Hazards
Primary Hazard: GB (Sarin) Nerve Agent
GB Characteristics:
- Colorless, odorless liquid (may have faint fruity odor in impure form)
- Highly volatile – rapidly evaporates to form toxic vapor
- Non-persistent – vapor hazard dissipates within hours under normal conditions
- Extremely toxic via inhalation, skin contact, and eye exposure
Toxicity:
- LCt50 (inhalation): Approximately 35-70 mg·min/m³
- LD50 (skin): Approximately 1,700 mg for a 70 kg person
- Lethal dose can be absorbed in seconds to minutes through vapor exposure
Routes of Exposure
- Inhalation: Most rapid and dangerous route; symptoms within seconds to minutes
- Skin Absorption: Liquid agent penetrates skin; vapor absorbed through eyes and mucous membranes
- Ingestion: Highly toxic if swallowed (unlikely route in field conditions)
Symptoms of Exposure
Mild Exposure:
- Miosis (pinpoint pupils)
- Rhinorrhea (runny nose)
- Tightness in chest
- Headache, nausea
Moderate to Severe Exposure:
- Severe difficulty breathing
- Excessive salivation and sweating
- Muscle twitching and tremors
- Convulsions
- Loss of consciousness
- Death from respiratory failure
Additional Ordnance Hazards
- Bursting Charge: Contains conventional explosive to rupture projectile and disperse agent
- Fuze Hazards: Standard point-detonating fuze presents explosive hazard
- Aged Munitions: Corrosion may have compromised projectile integrity; agent leakage possible
- Degradation Products: Aged GB may produce toxic degradation products
Environmental Factors
- Temperature: Higher temperatures increase volatility and vapor hazard
- Wind: Affects vapor dispersion and hazard area
- Terrain: Low-lying areas may accumulate vapor
- Persistence: Under normal conditions, GB vapor hazard dissipates within 24 hours; liquid agent may persist longer in sheltered areas
UXO/Chemical Ordnance Considerations
- Leaking Munitions: Any suspected leakage requires immediate evacuation and specialist response
- Corroded Rounds: Degraded projectiles may release agent without detonation
- Unknown Condition: Stockpile condition varies; some rounds may be severely degraded
- Dual Hazard: Both chemical and explosive hazards present simultaneously
Immediate Action (Suspected Exposure)
- Evacuate contaminated area immediately (move upwind and uphill)
- Remove contaminated clothing
- Wash exposed skin with soap and water or 0.5% bleach solution
- Seek immediate medical attention
- Nerve agent antidotes (atropine, pralidoxime) required for treatment
Key Identification Features
Dimensions
- Length: Approximately 400mm (15.7 inches) without fuze
- Diameter: 105mm (4.13 inches)
- Weight: Approximately 18 kg (39.7 lbs) complete
Color Scheme and Markings
Standard Chemical Ammunition Marking:
- Body Color: Gray
- Band: Green band (indicates chemical agent fill)
- Stenciling: Yellow markings
Specific Markings:
- “GB” or “SARIN” stenciled in yellow
- “GAS” marking
- Lot number and fill date
- Manufacturer codes
- Weight and fill information
WARNING: Old stockpile ammunition may have faded, obscured, or non-standard markings. Gray body with green band should always be treated as potential chemical munition regardless of legibility of stenciling.
Distinctive Features
- Gray Body Color: Distinguishes from HE (olive drab), smoke (green), and illumination (white)
- Green Band: Definitive indicator of chemical agent fill
- Burster Tube: Internal burster tube visible in sectioned training aids
- Fill Plug: May be visible on projectile body (used for agent fill)
Material Composition
- Body: Steel
- Rotating Band: Copper or gilding metal
- Fill: GB (Sarin) nerve agent
- Burster: TNT or similar explosive
- Fuze Well: Threaded steel
Comparison with Similar Rounds
| Feature | M60 GB | M60 HD | M60 VX | M60 HE |
|---|---|---|---|---|
| Body Color | Gray | Gray | Gray | Olive Drab |
| Band Color | Green | Green | Green | Yellow or None |
| Stenciling | Yellow “GB” | Yellow “HD” | Yellow “VX” | Yellow “HE” |
| Hazard | Nerve Agent | Blister Agent | Nerve Agent | Explosive/Frag |
Fuzing Mechanisms
Compatible Fuzes
- M557 Point-Detonating Fuze – Primary fuze; superquick or delay settings
- M572 Point-Detonating Fuze – Alternative
- Other standard 105mm PD fuzes compatible with chemical rounds
Function
The fuze functions identically to conventional HE rounds:
- Impact: Fuze strikes target
- Initiation: Firing pin activates detonator
- Detonation: Detonator initiates booster, which initiates burster charge
- Dispersal: Burster charge ruptures projectile body, dispersing agent as aerosol/droplets
Arming Sequence
- Bore Safety: Fuze safe until projectile exits gun tube
- Setback Arming: Acceleration forces begin arming sequence
- Spin Arming: Rotation completes arming process
- Armed: Fuze armed at safe distance from gun (typically 20-40 meters)
Superquick vs. Delay
- Superquick (SQ): Detonates immediately on impact; produces airburst-like dispersion
- Delay: Slight penetration before detonation; produces more concentrated ground contamination
Safety Mechanisms
- Standard bore-safe design
- Setback and spin arming requirements
- Interrupter mechanisms
UXO Fuze Considerations
- Aged fuzes may have degraded safety mechanisms
- Impact without detonation may have damaged fuze components
- Some fuzes may be armed but failed to function
- DO NOT approach – assume fuze is armed and sensitive
History of Development and Use
Development Background
The M60 GB was developed during the early Cold War as part of the U.S. Army’s chemical weapons modernization program. Following World War II, the U.S. recognized that chemical weapons had not been used in that conflict but remained a potential threat, particularly from the Soviet Union. The nerve agents (GB, VX) discovered during and after WWII represented a new generation of far more lethal chemical agents compared to WWI-era agents like mustard and phosgene.
Cold War Context
- Strategic Rationale: Deterrence and potential retaliation capability against Soviet chemical attack
- Tactical Concept: Non-persistent agents like GB were intended for offensive use, contaminating enemy positions briefly before friendly advance
- NATO Planning: Chemical weapons incorporated into NATO war plans as potential response to Warsaw Pact aggression
Stockpile History
The U.S. produced significant quantities of M60 GB rounds, which were stockpiled at:
- Tooele Army Depot, Utah
- Anniston Army Depot, Alabama
- Umatilla Chemical Depot, Oregon
- Aberdeen Proving Ground, Maryland
- Other continental U.S. and overseas locations
Non-Use Policy
Despite extensive stockpiling, the U.S. adopted a “no first use” policy for chemical weapons. The M60 GB and similar munitions were intended as a retaliatory capability rather than first-strike weapons.
Chemical Weapons Convention
The Chemical Weapons Convention (CWC), which entered into force in 1997, required the destruction of all chemical weapons:
- U.S. signed and ratified the CWC
- Destruction of chemical weapons stockpile mandated
- M60 GB rounds have been priority items for destruction
- Destruction methods include incineration and neutralization
Current Status
- Largely Destroyed: Majority of U.S. GB munitions have been destroyed
- Destruction Ongoing: Remaining stockpile destruction continues at designated facilities
- Legacy Sites: Potential for contamination at former storage and testing locations
- International: Other nations produced similar nerve agent artillery munitions
Never Used in Combat
The M60 GB was never used in combat by U.S. forces. The chemical weapons stockpile served its deterrent purpose through the Cold War and is now being eliminated under international treaty obligations.
Technical Specifications
| Specification | Detail |
|---|---|
| Caliber | 105mm |
| Projectile Length | ~400mm (15.7 in) without fuze |
| Weight (Complete) | ~18 kg (39.7 lbs) |
| Agent Fill | GB (Sarin) |
| Fill Weight | Approximately 1.36 kg (3 lbs) |
| Burster Charge | TNT or Tetryl, ~340g |
| Muzzle Velocity | Variable by propelling charge |
| Maximum Range | ~11,000m (12,000 yds) |
Agent Specifications (GB/Sarin)
| Property | Value |
|---|---|
| Chemical Name | Isopropyl methylphosphonofluoridate |
| Molecular Weight | 140.09 g/mol |
| Physical State | Colorless liquid |
| Vapor Pressure | 2.1 mmHg at 20°C |
| Volatility | 16,000 mg/m³ at 20°C |
| Persistence | Hours to ~24 hours (non-persistent) |
| Hydrolysis | Decomposes in water |
| Freezing Point | -56°C |
Contamination Characteristics
- Primary Hazard Duration: Hours under normal conditions
- Factors Affecting Persistence: Temperature, humidity, wind, terrain
- Decontamination: Hydrolysis, oxidizing agents, or weathering
Frequently Asked Questions
Q: Why is GB (Sarin) classified as a “non-persistent” agent, and what does this mean tactically? A: GB is classified as non-persistent because it evaporates rapidly under normal environmental conditions, with the vapor hazard typically dissipating within hours to about 24 hours. This is due to GB’s high volatility (tendency to evaporate). Tactically, this made GB suitable for offensive operations where the attacking force wanted to contaminate enemy positions but then occupy that terrain shortly afterward—the hazard would have largely dissipated by the time friendly forces arrived. In contrast, persistent agents like VX or HD remain hazardous for days to weeks, making them better suited for area denial or defensive barriers where no friendly occupation is intended.
Q: How can the M60 GB be distinguished from conventional high explosive (HE) 105mm rounds in the field? A: The M60 GB has several distinguishing features: (1) Body color is gray rather than the olive drab of HE rounds; (2) Green band around the body indicates chemical agent fill; (3) Yellow stenciling includes “GB,” “GAS,” or “SARIN” markings. However, field identification can be complicated by weathering, corrosion, and faded markings. Any gray projectile with a green band, or any 105mm round with illegible markings, should be treated as a potential chemical munition until verified by qualified specialists. Never rely solely on visual identification—when in doubt, evacuate and report.
Q: What is the difference between the M60 GB and the M60 VX projectiles given both contain nerve agents? A: While both contain nerve agents, they have very different tactical characteristics. GB (Sarin) is non-persistent and primarily a vapor hazard—it evaporates quickly, creating an immediate but short-duration threat. VX is persistent and primarily a contact hazard—it evaporates very slowly and remains dangerous on surfaces for days to weeks. GB was intended for targets that would be quickly occupied by friendly forces; VX was intended for long-term area denial. VX is also significantly more toxic than GB when absorbed through the skin, while GB creates a more immediate inhalation hazard due to its higher volatility.
Q: What should EOD or first responder personnel do upon discovering a suspected M60 GB projectile? A: The response protocol for suspected chemical munitions is significantly more restrictive than for conventional ordnance: (1) Do not approach any closer than the initial observation distance; (2) Note any signs of leakage (discoloration, liquid, unusual odors, dead vegetation/animals); (3) Evacuate all personnel from the immediate area (minimum 500-meter radius, larger if leakage suspected); (4) Establish upwind observation point and restrict access; (5) Report immediately to military chemical warfare specialists or qualified civilian hazmat authorities; (6) Do not attempt any render-safe procedures—chemical ordnance requires specialized personnel and equipment. Standard EOD protocols are insufficient for chemical munitions.
Q: Why were chemical weapons like the M60 GB stockpiled if there was a “no first use” policy? A: The stockpile served as a deterrent and retaliatory capability. The Cold War doctrine recognized that the Soviet Union possessed extensive chemical weapons capabilities. The U.S. stockpile existed to: (1) Deter Soviet first use of chemical weapons by ensuring a retaliatory capability; (2) Provide a response option if chemical weapons were used against U.S. or allied forces; (3) Ensure NATO forces were not at a tactical disadvantage if chemical warfare occurred. The deterrent effect was considered successful—neither side used chemical weapons during the Cold War. The Chemical Weapons Convention now prohibits this approach, requiring destruction of all stockpiles.
Q: How is the M60 GB projectile destroyed under Chemical Weapons Convention protocols? A: The U.S. has employed multiple destruction methods: (1) Incineration – The most common method, where assembled munitions or drained agent are burned in specialized incinerators with pollution controls; (2) Neutralization – Agent is chemically treated to render it non-toxic, often using hot water and sodium hydroxide; (3) Explosive destruction – Munitions are destroyed using controlled detonation in specialized chambers that capture and treat the agent. All methods must meet strict verification and environmental standards under CWC supervision. The destruction process is slow and expensive due to the safety requirements, which is why complete elimination of Cold War stockpiles has taken decades.
Q: Could aged M60 GB projectiles be leaking agent, and how would this be detected? A: Yes, aged chemical munitions can leak due to corrosion of the projectile body, degradation of seals, or crystallization of agent around fill plugs. Detection indicators include: (1) Visual signs – discoloration, crystalline deposits, or liquid around seams and plugs; (2) Environmental effects – dead vegetation, dead insects/animals near the munition; (3) Odor – though GB is nearly odorless, impurities or degradation products may have detectable odors; (4) Chemical detection equipment – Military and hazmat teams use detection papers, tubes, and electronic detectors that can identify nerve agents at low concentrations. Any suspected leakage requires immediate evacuation and specialist response. Never sniff or closely approach suspected chemical munitions to check for odors.
Q: What makes nerve agents like GB more dangerous than traditional chemical weapons like mustard gas? A: Nerve agents like GB are far more toxic than WWI-era agents. Specifically: (1) Toxicity – GB is approximately 500 times more toxic than chlorine and significantly more toxic than mustard by inhalation; (2) Speed of action – Symptoms occur within seconds to minutes, versus hours for mustard; (3) Mechanism – Nerve agents disrupt the nervous system, causing loss of body function control and respiratory failure; mustard primarily causes painful blisters and respiratory damage over time; (4) Protection requirements – The extreme toxicity of nerve agents requires higher levels of protective equipment. However, mustard has advantages as a casualty agent in that it produces extensive long-term casualties and its persistence creates sustained area denial.
Q: What historical events led to the development and stockpiling of nerve agents like GB? A: Nerve agents were discovered by German scientists in the 1930s while researching pesticides. Germany produced but did not use nerve agents in WWII. After the war, Allied forces captured German nerve agent stocks and production knowledge. The Cold War created pressure to develop retaliatory capabilities against the Soviet chemical threat. The U.S. began nerve agent production in the 1950s, leading to weapons like the M60 GB. Key events shaping the program included: (1) Soviet chemical weapons development; (2) Korean War concerns about chemical attack; (3) NATO doctrine incorporating chemical response options; (4) The arms race mentality of mutually assured destruction. The program continued until international pressure and the CWC led to the decision to destroy all stockpiles.
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.