NATO 155mm M107 HE Projectile

Overview

The 155mm M107 High-Explosive (HE) Projectile is the standard NATO general-purpose artillery round that has served as the backbone of Western medium artillery for over six decades. First standardized in the late 1950s, the M107 provides a balance of blast and fragmentation effects suitable for engaging personnel, light fortifications, unarmored vehicles, and area targets. Its widespread adoption across NATO and allied nations has made it one of the most produced and deployed artillery projectiles in history. The M107 remains in active service worldwide despite the development of more modern extended-range and precision-guided alternatives, owing to its proven effectiveness, massive existing stockpiles, and low cost.

Country/Bloc of Origin

• Primary Origin: United States of America
• Development Period: 1950s
• Design Authority: U.S. Army Ordnance Corps
• Primary Manufacturers: U.S. ammunition plants; numerous licensed producers worldwide
• NATO Standardization: Adopted as standard 155mm HE projectile across NATO
• International Production: Manufactured under license in dozens of countries
• Export Status: Widely exported; one of the most globally distributed artillery projectiles
• Current Status: Remains in production and active inventory with U.S., NATO, and allied forces worldwide

Ordnance Class

• Type: Artillery projectile
• Primary Role: High-explosive, general-purpose bombardment
• Delivery Method: Gun-launched from 155mm howitzers and guns
• Category: Conventional ammunition, separate-loading (semi-fixed in some configurations)
• Fire Support Role: General fire support, counter-battery fire, suppression, destruction of field fortifications, anti-personnel, anti-materiel
• Tactical Level: Battalion through corps-level artillery fire support

Ordnance Family/Nomenclature

Primary Designation:

• U.S. Designation: M107
• Full Nomenclature: Projectile, 155mm, HE, M107
• NATO Stock Number (NSN): 1315-00-028-9529 (representative; varies by configuration)

Designation Variants:

• M107: Standard HE projectile
• M107A1: Improved variant
• M107A2: Further improvements
• M795: Improved insensitive munition HE (newer production)

Related Projectile Family:

• M549/M549A1: Rocket-Assisted Projectile (RAP) for extended range
• M483/M483A1: Dual-Purpose Improved Conventional Munitions (DPICM) – cargo projectile
• M692/M731: Family of Anti-Personnel (FASCAM) mines cargo
• M712 Copperhead: Laser-guided projectile
• M982 Excalibur: GPS-guided extended-range projectile
• M795: Insensitive munition replacement for M107

Compatible Weapon Systems:

• M109 family self-propelled howitzer (all variants through M109A7)
• M777 lightweight towed howitzer
• M198 towed howitzer
• M114 towed howitzer (historical)
• M59 Long Tom (historical)
• FH70 towed howitzer
• G5/G6 series (South African)
• AS90 (British)
• PzH 2000 (German)
• K9 Thunder (South Korean)
• All NATO-standard 155mm systems

Propellant Configurations:

• M3A1 (White Bag): Zones 1-5
• M4A2 (Green Bag): Zones 3, 5, 7
• M119 Series: Modular artillery charge system (MACS)
• M203 Series: Propelling charge for extended-range platforms

Hazards

Primary Hazards:

Blast Effect:

• High overpressure wave causes fatalities and injuries at close range
• Structural damage to light fortifications and buildings
• Vehicle damage within blast radius

Fragmentation:

• Primary Lethal Mechanism: Steel body produces numerous high-velocity fragments
• Lethal Radius: Approximately 50 meters
• Casualty Radius: 100+ meters
• Fragment Danger Radius: 200-300+ meters
• Fragment Velocity: Approximately 1,500+ m/s at detonation

Ground Effects:

• Crater formation
• Secondary debris and spall
• Ground shock

Sensitivity Factors:

• Fuze Sensitivity: Point-detonating fuzes are impact-sensitive when armed
• Proximity Fuze: Electronic fuzes sensitive to radio frequency interference
• Booster Sensitivity: Booster explosive charge is sensitive to shock
• Main Charge Stability: TNT/Composition B main fill generally stable

UXO Hazards:

• Dud Rate: Varies with fuze type, impact conditions, and ammunition age
• Partial Arming: Impact may leave fuze in armed or partially armed condition
• Ground Penetration: Soft soil may prevent fuze functioning
• Damaged Fuzes: Impact damage may leave fuze in unpredictable state
• Booster Exposure: Fuze removal during demining operations creates booster hazard

Environmental Considerations:

• Temperature Extremes: Prolonged storage outside rated temperatures affects performance
• Corrosion: Steel body and fuze components susceptible to corrosion
• Age: Older ammunition may have degraded explosive fill or fuze components
• Propellant Degradation: Separate propellant charges can become unstable with age

Key Identification Features

Dimensions:

• Length (projectile body): Approximately 605mm (23.8 inches)
• Diameter: 155mm (6.1 inches)
• Total Weight (projectile): 43.2 kg (95.2 lbs)

Physical Characteristics:

• Nose: Ogival (curved) profile with fuze well
• Body: Cylindrical forged steel shell
• Base: Flat or boat-tailed depending on variant
• Rotating Band: Copper alloy, positioned near base
• Bourrelet: Machined bearing surface near nose
• Base Plug: Threaded plug closing base opening (manufacturing access)

Color Schemes (U.S./NATO Standard):

• Body Color: Olive drab (OD)
• Markings: Yellow or white stenciling
• Fuze Marking Area: May include colored bands indicating specific fuze compatibility

Marking System:

• Nomenclature: “PROJ 155MM HE M107” or similar
• Lot Number: Manufacturing batch identification
• Date: Manufacture date (month/year)
• Weight Zone: Square symbol with weight classification (important for fire control)
• Manufacturer Code: Production facility identifier
• Explosive Fill: “COMP B” or “TNT” indicating main charge type
• NSN: May include NATO stock number

Weight Classification System: The M107 uses a weight zone classification system indicated by a square symbol containing a number:

• Zone 1: Lightest projectiles
• Zone 4: Nominal weight
• Zone 7: Heaviest projectiles Fire direction centers use weight zone for precise ballistic calculations.

Distinctive Features:

• Single rotating band
• Ogival nose with standard fuze well
• Relatively thick-walled steel construction
• Standard NATO fuze threading
• Square weight zone marking

Fuzing Mechanisms

Standard Fuze Options:

M557 Point-Detonating Fuze:

• Super-quick (SQ) mode for surface burst
• Delay mode (0.05 seconds) for penetration
• Most common field fuze

M739/M739A1 Point-Detonating Fuze:

• Similar functions to M557
• Improved reliability

M582 Mechanical Time/Super-Quick Fuze:

• Point-detonating with time option
• Allows airburst missions

M728/M732 Proximity Fuze:

• Electronic variable time (VT)
• Airburst at optimum height above target
• Battery-powered radio frequency sensor

M762/M767 Multi-Option Fuze:

• Proximity, super-quick, and delay functions
• Modern electronic fuze system

Arming Sequence:

1. Loading: Fuze set per fire mission requirements
2. Setback: Propellant ignition creates acceleration; setback force releases primary safety
3. Spin-Up: Rifling engagement creates rotation; centrifugal force acts on arming mechanism
4. Muzzle Exit: Projectile clears tube at high velocity
5. Arm Distance: Fuze completes arming sequence after safe distance (typically 18-200 meters depending on fuze type)
6. Flight: Projectile follows ballistic trajectory
7. Terminal: Fuze functions based on mode:
   • SQ: Nose impact triggers instant detonation
   • Delay: Impact triggers delay element, then detonation
   • Proximity: Radio altimeter triggers at preset height
   • Time: Mechanical timer triggers at preset time

Explosive Train:

1. Fuze detonator (initiated by firing pin or electronic pulse)
2. Lead/booster explosive (amplifies initiation)
3. Booster charge (typically tetryl or PBXN)
4. Main charge (TNT or Composition B)

Safety Features:

• Bore Safety: Multiple interlocks prevent in-bore detonation
• Setback Lock: Requires acceleration force to release
• Spin Rate Lock: Requires minimum rotation for arming
• Arm Distance: Fuze will not function until safe distance from gun

History of Development and Use

Development Background: Following World War II, the U.S. Army undertook comprehensive standardization of artillery calibers and ammunition. The 155mm howitzer emerged as the primary medium artillery piece, replacing the diverse mix of wartime equipment. The M107 was designed as the standard high-explosive projectile to arm the growing fleet of 155mm systems.

Historical Timeline:

• 1950s: M107 development and standardization
• 1963: M109 self-propelled howitzer enters service with M107 as primary ammunition
• Vietnam War: Extensive combat employment
• 1970s-1980s: NATO-wide adoption; massive Cold War stockpiling
• 1991 Gulf War: Primary artillery ammunition
• 2000s-Present: Continued use in Iraq, Afghanistan, Syria operations
• Ongoing: Remains in production; M795 insensitive munition variant supplements

Combat Employment:

Vietnam War (1965-1973):

• Primary fire support ammunition
• Millions of rounds expended
• Employed from fire support bases and mobile positions
• Used for harassment and interdiction (H&I) fires

Arab-Israeli Wars:

• Used by multiple parties (U.S. supply to Israel; various sources to Arab states)
• Extensive artillery duels

Gulf War (1991):

• Massive artillery preparation
• Counter-battery fire missions
• Fire support for ground offensive

Iraq and Afghanistan (2001-2021):

• Fire support for ground operations
• Counter-insurgency missions
• Firebase defense
• Illumination and smoke missions using related projectiles

Ukraine Conflict (2022-present):

• Significant NATO supply of 155mm ammunition including M107
• Extended-range and precision variants prioritized where available
• Standard M107 remains bulk fire support ammunition

Production and Stockpiles:

• Produced in enormous quantities during Cold War
• Multiple nations maintain large strategic reserves
• Active production continues to replenish wartime consumption
• Estimated billions of rounds produced globally

Impact on Artillery Doctrine: The M107’s standardization enabled NATO interoperability—any NATO 155mm howitzer can fire any NATO member’s M107 ammunition. This logistics compatibility transformed alliance artillery operations and remains a cornerstone of collective defense.

Technical Specifications

Specification	Value
Caliber	155mm (6.1 inches)
Projectile Weight	43.2 kg (95.2 lbs)
Projectile Length	~605mm (23.8 in)
Explosive Fill Type	TNT or Composition B
Explosive Weight	6.62 kg (14.6 lbs) TNT equivalent
Muzzle Velocity (Zone 5)	~564 m/s
Muzzle Velocity (Zone 8)	~684 m/s
Maximum Range (M109A6)	~18,100 m (Zone 8 white bag)
Maximum Range (M109A6, Zone 8S)	~22,000 m
Maximum Range (M777, M203)	~24,000+ m
Lethal Radius	~50 m
Casualty Radius	~100+ m
Fragment Danger Radius	~200-300 m
Fuze Thread	Standard U.S./NATO 2″ – 12UN-2A
Operating Temperature	-40°C to +63°C

Range by Propellant Charge (M109A6 Example):

Charge	Zone	Approximate Range
M3A1 (White Bag)	3	~8,000 m
M3A1 (White Bag)	5	~11,500 m
M4A2 (Green Bag)	7	~15,000 m
M4A2 (Green Bag)	8	~18,100 m
M203 (Extended)	8S	~22,000 m

Frequently Asked Questions

Q: Why has the M107 remained in service for over 60 years? A: The M107 has persisted due to several factors: (1) proven combat effectiveness for general fire support missions, (2) massive existing stockpiles representing enormous investment, (3) universal NATO compatibility enabling logistics interoperability, (4) acceptable cost compared to precision-guided alternatives, and (5) continued utility for area suppression missions where precision guidance is unnecessary. While supplemented by modern projectiles like the M982 Excalibur, the M107 remains cost-effective for high-volume conventional fires.

Q: How does the M107 compare to the Soviet OF-540? A: The M107 and OF-540 are broadly comparable general-purpose HE projectiles of similar era and purpose. The M107 (155mm) carries approximately 6.62 kg of explosive compared to 5.86 kg in the OF-540 (152mm). Both produce similar fragmentation effects. Maximum ranges depend on the firing system and propellant rather than the projectile alone. The primary difference is caliber, reflecting the Western (155mm) and Soviet (152mm) artillery standardization decisions made in the mid-20th century.

Q: What is the difference between M107 and M795? A: The M795 is a newer-production HE projectile designed as an Insensitive Munition (IM) to reduce the risk of unintended detonation during transport, handling, and storage. The M795 uses IM-compliant explosive fill that is less sensitive to impact, heat, and fragment attack than the traditional Composition B fill in the M107. Ballistically, the M795 is similar to the M107, allowing interchangeable tactical employment while improving ammunition safety throughout the logistics chain.

Q: What fuze type provides the most lethal effect against exposed personnel? A: Proximity (VT) fuzes like the M732 provide optimum lethality against exposed personnel by detonating the projectile at an ideal height above the ground (typically 5-10 meters). This airburst creates a downward-spreading fragment cone that defeats prone and covered positions more effectively than impact-detonated rounds. Point-detonating fuzes with super-quick mode are effective against standing personnel but lose effect against prone targets due to the largely horizontal fragment pattern.

Q: How is the weight zone marking used in fire direction? A: The weight zone system classifies individual projectiles by actual weight compared to the nominal design weight. Fire direction centers input the weight zone when computing firing data because projectile weight affects ballistic trajectory. Heavier projectiles (higher zones) have slightly shorter range; lighter projectiles travel slightly farther. Accurate weight data improves first-round accuracy. The square symbol on the projectile body contains a number (typically 1-7) indicating the weight zone.

Q: What determines whether to use delay or super-quick fuze setting? A: Super-quick (SQ) mode detonates instantaneously on surface contact, maximizing blast and fragmentation effect at ground level—optimal for personnel, thin-skinned vehicles, and above-ground structures. Delay mode (typically 0.05 seconds) allows the projectile to penetrate earth, light cover, or structures before detonating, creating subsurface explosions for bunker busting or defeating defilade positions. Fire mission requirements and target type determine the appropriate setting.

Q: How many M107 rounds are needed to suppress a typical target? A: Target suppression depends on target type, size, protection level, and desired effect. Doctrinal planning factors vary, but typical examples include: (1) personnel in the open: 1-2 rounds per hectare for suppression, (2) personnel in fighting positions: 6-10 rounds per hectare, (3) light fortifications: 20-40 rounds per position. Modern fire direction systems calculate precise ammunition requirements based on target characteristics, ammunition type, fuze selection, and desired damage probability.

Q: What is the UXO threat from M107 projectiles? A: M107 UXO presents significant hazards due to the large explosive content (6.62 kg) and potentially armed fuze. Dud rates vary based on fuze type, impact conditions, and ammunition age—typically estimated at 2-15% depending on circumstances. Soft soil impacts frequently prevent fuze functioning. Damaged fuzes may be extremely sensitive or unpredictable. All suspected UXO should be marked, area evacuated, and reported to qualified EOD personnel. Never approach, touch, or attempt to move suspected artillery UXO.

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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.