AN M18

The M18 Colored Smoke Grenade is a U.S. Army grenade used as a ground-to-ground or ground-to-air signaling device, a target or landing zone marking device, or a screening device for unit maneuvering. It entered service in 1942 and has been the primary colored smoke grenade for the U.S. Army since.

History

The M18 was developed in 1942 during World War II and was completed in November of that year. It was designed to replace the M16 smoke grenade, which did not burn as long or as vividly. It was designated standard issue in the fall of 1943. Both were produced at the same time as the M16 production lines were already setup when the M18 was adopted.

The M16 was available in red, orange, yellow, green, blue, violet, and black. The M18 initially were going to be produced in the same colors, including white, but it was decided to limit it to four colors (red, yellow, green and violet) for simplicity. The M16 was declared limited standard in 1944 but was still available when it was declared obsolete in the early 1990s.

During the Vietnam War, the M18 was mainly used by troops for signaling to helicopters and other aircraft. Red typically meant danger, while violet and yellow were used to mark pickup zones and friendly force locations. Green was rarely used due to it being difficult to spot. However, color coding and usage varied by squad.

In 1971, a non submersible version of the M18 was under testing as the M18 provided poor signal when used in areas partially or fully covered in water. This made the standard M18 ineffective in such areas in Vietnam. This version of the M18 had a silicon ballute which acted as a parachute and flotation device. It was produced by Northrup Carolina, a subsidiary of Northrup Grumman at the time.

By June 2019 the Pine Bluff Arsenal has produced 3,888,502 M18 grenades since its introduction.

In 2022, the US supplied Ukraine with an undisclosed amount of M18 smoke grenades as part of a military aid package.

Design

The early M18 has a 5.75" x 2.50" steel cylindrical outer casing with a M200A1 or M200A2 pull-ring fuze assembly and four emission holes on the top that were covered by tape. On the bottom is an additional hole for smoke to release when ignited.The body contains a primer, and starter/ignition mixture. Below that is a pyrotechnic delay column surrounded by donut shaped smoke filler mixture that varied in composition depending on the color used. Including filling, the M18 weighed 19 oz.

The M18 was light gray, with yellow text painted stating the color. It came shipped in a metal tube used to protect it from moisture.
The M18 came in four variations: G940 (Green), G945 (Yellow), G950 (Red), and G955 (Violet).

Later M18 versions came with an M201A1 pull-ring fuze assembly in an olive drab body with the top painted indicating the color and white text with a band towards the bottom. One version removed the bottom emission hole, keeping the four on the top, while the most recent version removed the top emission holes and had one on the bottom. Instead of a metal tube a wax/cardboard tube was used for shipping.

In 2006 wafer starter patches were added inside the body between the donut shaped pucks of dye which improved burn times.

Non-submersible Variant

The non submersible M18 was the same size as the standard M18 and looked almost identical on the outside. The body contains a chimney design vent hole under the fuze in the middle. Surrounding the chimney is a folded silicone fiberglass ballute that is attached to a bulkhead plate. 8 vent holes on the top of the bulkhead are used to inflate the ballute when the grenade is ignited. Below the bulkhead is a starter/ignition mixture, inflation mixture, and smoke mixture.

When ignited and thrown, the top of the grenade with the pull-ring fuze assembly detached while the ballute inflated. The grenade would then glide towards the ground upright, and could float in water.

It was found these versions of the M18 had a lower smoke volume but burning time was almost double the standard M18 with 90 seconds minimum.

Usage

The M18 is used by holding it in one hand with the safety lever pressed against the canister. The safety pin/ring is then removed and the M18 can be thrown. As the safety lever is released, it is forced away from the body by a striker spring. The striker rotates on its own and strikes the percussion primer. The fuze delay then starts the ignition process. The tape covering the bottom emission hole is blown off and smoke is released. After ignition, the M18 produced a cloud of colored smoke for 50 to 90 seconds. The M18 could be thrown up to 35 meters by the average soldier.

If the fuze was non-functional, the M18 could still be used. This was done by removing the tape covering the hole on the bottom, removing the fuze assembly, and igniting the starter mixture with an open flame.

With the M18 there is a danger of starting a fire if it is used in a dry foliage area as the tube gets very hot during the burning process. Expended smoke grenade canisters remain hot for some time after burning out and should not be picked up bare-handed.

Chemistry

The smoke from an M18 is produced by volatilizing and condensing a colored dye mixture. The heat produced by the starter mixture volatilizes the dye which is then condensed by the air forming a colored smoke cloud. A cooling agent is added to the smoke mixture to help prevent excessive decomposition of the dye while burning time can be regulated by adjusting the amount of oxidant and combustible materials.

In the original M18 chemical components, sulfur was used for the starter mixture with sodium bicarbonate as a coolant. Smoke mixture was dependent on the color of smoke being produced.

The formula for the M18 was later changed in the late 90s due to health and environmental concerns. The new M18 used sugar for the starter mixture and magnesium carbonate as coolant. The smoke mixtures were also changed, using different dyes.

New yellow and green M18 were made with relative ease, while red and violet were more challenging to produce. Early attempts failed due to insufficient flaming/smoke production of the mixtures. Additionally the new red formula produced a pink smoke rather than the intended red. Several attempts were made to correct it but were unsuccessful.

The smoke produced by an M18 is harmful if inhaled, even with the new less toxic smoke mixtures. In enclosed spaces the grenade displaces oxygen due to the burning process and can cause respiratory or oxygen deprivation.

The new dye mixtures are produced by Nation Ford Chemical in South Carolina.

Old/New Mixture Comparison Table

Manufacturing

The Pine Bluff Arsenal in Arkansas is the only manufacturer of the M18 today. It has been assembled there since its introduction in 1942. Majority of M18's were produced by Pine Bluff. This is denoted on an M18 by a "PB" before the lot number marked on the outside. The various components of the M18 are made by different manufacturers contracted yearly in the United States. As of 2024 the body and lid are made by Tool Masters, Inc. in Tuscumbia, Alabama. The fuze assembly is made by Day & Zimmermann in Texarkana, Texas. The smoke mixture dyes are produced by Nation Ford Chemical in South Carolina.

During the Vietnam War, the M18 was also manufactured by Martin Electronics, Inc. ("MEI") in Florida and Talley Industries, Inc. ("TAC") in Arizona.

Unit Costs/Year

Users

*
* : Was used in the Vietnam War.: 45,46
* : Was used by Iraqi security forces; provided by United States.
* : Used for army training exercises.
* : Was used in the Vietnam War.
* : Received as part of military aid packages from the United States during the Russo-Ukraine War in 2022.

Image Gallery

File:100222-F-1735C-029 (4389508026).jpg, Smoke billowing from a red M18.
File:US Marines 100520-M-9232S-012 M18 green smoke grenade crop.jpg, Smoke billowing from a green M18.
File:VI zmiana PKW Afganistan (25).jpg, Smoke billowing from a yellow M18.
File:NARA 111-CCV-349-CC43096 Smoke grenade identifies landing zone for 101st Airborne UH-1D carrying brigade commander Operation Cook 1967.jpg, Violet M18 used to identify landing zone (Vietnam 1967)
File:Company C, 1st Battalion, 8th Cavalry commander communicates with a command helicopter.jpg, U.S. Army radio operator with multiple M18 grenades (Vietnam 1966)
File:Run DVIDS389903.jpg, Green M18 used for cover during training exercise (Hawaii 2010)
File:US- Solder.jpg, U.S. Army Paratrooper with yellow M18 visible (Iraq 2004)
File:Company C, 2nd Battalion, 27th Infantry radioman's pack.jpg, U.S. Army radio operator with M18 grenades (Vietnam 1968)

Media use

*The use of violet-colored M18 Smoke Grenades can be seen during the "Purple Haze" scene, in the film ''Apocalypse Now'' (1979).

See also

*United States hand grenades
* AN-M8 smoke grenade
*

External links

Pine Bluff Arsenal Video News Release - YouTube

Pine Bluff Arsenal Command Video - YouTube

Vietnam War - Popping Red Smoke For Patrol Extraction 1967 - YouTube

References

{{DEFAULTSORT:M18
Smoke grenades
Hand grenades of the United States