Description
105mm ICM Projectile with M577A1 MTSQ Nose Fuze
This inert 105mm ICM projectile is supplied with an M577A1 mechanical time and superquick nose fuze. The supplied projectile designation is XN400E1. ICM stands for Improved Conventional Munition, a class of artillery ammunition designed to carry smaller submunitions. The projectile and included fuze make this a collectible for those studying U.S. artillery ammunition and mechanical fuze design.
Identification and Features
The projectile model and fuze model identify separate parts of the assembly. MTSQ describes the fuze's mechanical time and superquick functions. Army manuals describe the M577 series with three numbered timing dials viewed through a side window. The A1 suffix identifies a revised model within the M577 series.
- Caliber: 105mm
- Supplied projectile designation: XN400E1
- Listed ammunition type: Improved Conventional Munition (ICM)
- Included nose fuze: M577A1
- Fuze type: Mechanical Time and Superquick (MTSQ)
- Documented M577A1 assembly drawing: 9352381
- Status: Inert collectible
Function
In military service, ICM projectiles carried small grenades that were released over a target area. The time fuze controlled when the payload was released. The M577A1 used a clockwork timing mechanism and also had an impact function. Army manuals identify it as a fuze for base-ejection ammunition, in which the contents leave through the rear of the projectile.
Documented Applications
Army operator manuals list the M444 as a standard 105mm ICM cartridge for the M101A1 and M102 howitzers. Those cartridges used specially modified M548 or M565 fuzes. Separately, Army ammunition data document the M577A1 family for payload-ejection ammunition in 105mm, 155mm, 8-inch, and 4.2-inch sizes. These records establish the wider artillery applications of ICM ammunition and the included fuze family; each projectile model had its own approved fuze combination.
Product History
The standard 105mm M444 ICM cartridge was classified for service in 1961, placing this ammunition class within Cold War artillery development. The included fuze belongs to a later design generation. Army records list the original M577 as Standard A in March 1973 and the M577A1 as Standard A in June 1984. The A1 version changed the impact mechanism and used a zinc nose section with an aluminum lower body.
Equipment History
The U.S. 105mm howitzer family that fielded ICM ammunition included the M101A1 and M102. The M101 family grew from the M2A1, first produced in 1940 and widely used during World War II. Rock Island Arsenal made its carriage and recoil equipment. In the early 1960s, the arsenal developed carriage and recoil components for the lighter M102. Its wishbone-shaped carriage allowed a full circle of traverse, and the weapon could be moved by truck or air transport. The M119 later replaced the M102 in artillery battalions.
Weapon-System Background
Light field howitzers supplied artillery support to ground troops. Their ammunition families included high explosive, smoke, illumination, and specialized antipersonnel cartridges. Many 105mm howitzer cartridges were semifixed, meaning the projectile could be separated from its cartridge case. ICM added a carrier-shell design to this ammunition family. Early ICM models used antipersonnel grenades, while later dual-purpose ICM designs combined fragmentation and an antiarmor effect. These terms describe different generations of ammunition and are important when comparing projectile models.
History of Use
105mm ICM ammunition saw combat use during the Vietnam War. A historical briefing prepared by Picatinny Arsenal includes 105mm ICM in its comparison of ammunition used in that conflict. The Army studied its effects alongside conventional shells in 105mm, 155mm, and 8-inch calibers. Its place in Army service continued beyond that period: M101A1 and M102 operator manuals from the following decades still listed M444 ICM ammunition among their authorized cartridges. This is the documented service background of the broader ammunition family.
Condition
The projectile and included M577A1 nose fuze are inert. The listed assembly is intended for collection, display, and historical study, with the fuze included as part of the projectile.
Ideal For
Suitable for collectors of U.S. artillery projectiles, mechanical fuzes, and specialized ammunition. It can accompany technical manuals and other inert examples in a reference collection focused on ICM development. The included M577A1 also makes it useful for displays comparing time-fuze designs and changes in artillery ammunition during the Cold War.
- U.S. artillery ammunition collectors
- ICM reference collections
- Mechanical fuze studies
- Cold War ordnance displays
- Military history exhibits
Approx length 23", Approx width 4.5", Approx height 4.5", Approx weight 21.6lbs.
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