Description
Vietnam-Era U.S. Army FT 155-AH-1 Graphical Firing-Table Set for 155mm M118 Illumination
Item Overview
This Vietnam-era U.S. Army FT 155-AH-1 graphical firing-table set is a portable analog calculator for 155mm artillery fire direction. It was made for the M118 illuminating projectile used with an M501 time fuze and the original M109 self-propelled howitzer family. Fire-direction personnel used its calibrated rules and clear cursor to turn chart range and desired burst height into howitzer elevation and fuze-setting data. This is fire-control equipment. It is not ammunition, a fuze, a gun sight, or a component installed inside a projectile.
Identification and Features
The set is identified by its FT 155-AH-1 marking, period Federal Stock Number, and Ordnance part number. The reported Charge 3 “Green Bag” and Charge 6 markings represent one face of each included rule. Period FM 6-40 states that the opposite faces add Charge 5 Green Bag and Charge 7 data. The rule is dated April 1964, while the original carton is marked July 1965. The carton date is a package marking and should not replace the date printed on the rule. Its 11-digit FSN is correct for the federal supply system used before modern 13-digit NSNs.
- Official designation: FT 155-AH-1
- Equipment type: Two-rule graphical firing table and analog ballistic calculator
- Projectile application: 155mm M118-series illuminating projectile
- Service fuze: M501-series mechanical time and superquick fuze, used in time mode for illumination
- Weapon application: M126 and M126E1 155mm cannons on the original M109 howitzer family
- Reported visible rule faces: Charge 3 “Green Bag” and Charge 6
- Period two-rule coverage: Charges 3 and 5 Green Bag; Charges 6 and 7
- Federal Stock Number: FSN 1220-764-5420
- Ordnance part number: A10533324
- Rule date: April 1964
- Carton marking: July 1965
- Carrying case: CASE, CARRYING M108
- Included components: Two rule bodies, transparent cursor, carrying case, and original carton
- Status: Non-energetic fire-control equipment
Original Service Function
The graphical firing table gave trained fire-direction personnel a fast way to prepare firing data. The computer selected the rule for the propelling charge and moved the cursor hairline to the required range. The scales then showed the quadrant elevation and time-fuze setting for the selected height of burst. Army doctrine used a normal burst height of about 750 meters above the area for the M118. Personnel adjusted that figure for the height difference between the battery and target. The rules also covered different parts of the projectile’s flight and several charge choices. This reduced the time needed to work through full printed firing tables during a mission.
M118 Illuminating Projectile and M501 Fuze
The M118 was a base-ejection 155mm illuminating projectile. Its service payload was a bright flare suspended below a parachute. When a live M501 fuze reached its set time, it started the base-ejection sequence that released the flare and parachute. The slowly descending flare lit the ground for observation, troop movement, or other fire missions. The live M501 was a mechanical time and superquick fuze, but crews used its time function for illumination. This listing does not include an M118 projectile, M501 fuze, propelling charge, or any energetic material.
M109 Howitzer Application
The FT 155-AH-1 family supported the original M109 155mm self-propelled howitzer fitted with the M126 or M126E1 cannon. A 1965 Army firing-table record lists these cannons with M118-series illuminating projectiles. The tracked M109 gave field artillery a protected and mobile gun with a fully rotating turret. It could move with armored and mechanized forces, then provide indirect fire from a new position. Later M109 versions received longer cannons and improved fire-control equipment. This set belongs to the short-barrel, first-generation M109 period.
Historical Background and Service Use
The U.S. Army adopted graphical firing tables during World War II to speed field artillery calculations. By the 1960s, fire direction centers combined map plots, firing charts, weather corrections, and charge-specific rules to prepare data for the gun line. The Army published its first M109 section manual in December 1962, and the new howitzer entered service during the early 1960s. M109 units later served in Vietnam, where mobile 155mm artillery supported bases and field operations. Illuminating fire helped observers and troops watch movement, mark areas, and coordinate night missions. The April 1964 rule date and July 1965 carton marking place this set in that Vietnam-era system. Those dates do not prove that this exact set was carried in Vietnam.
Condition and Completeness
This surplus set appears substantially complete with both double-sided rule bodies, the transparent cursor, the M86 carrying case, and the original carton. Expect scratches, scuffs, fading, stains, writing, edge wear, small dents, or other signs of age and storage. Printed scales, dates, package markings, and minor details may vary within inventory. No claim is made that the scales remain accurate for operational fire direction. This listing is for one display set only. The M109 howitzer, M118 projectile, M501 fuze, and manuals are not included. Please check the pictures for the general condition of the item.
Ideal For
This set is well suited for collections and exhibits about Vietnam-era artillery, manual fire direction, the original M109 howitzer, and the history of analog military computing.
- Vietnam War artillery displays
- U.S. Army fire-direction collections
- Original M109 and M126 cannon exhibits
- 155mm ammunition-support displays
- Analog military-computing collections
- Museums and educational exhibits
Approx length 18", Approx width 5", Approx height 1", Approx weight 1.1lbs.
Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item’s general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.
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