Mechanical clock-type fuzes with impact action

The M501A1 and M501 fuzes are mechanical, clock-type fuzes with both impact and time-based dual-action functions. They are used with artillery shells for 105 mm and 155 mm howitzers, as well as mortars with calibers from 105 mm.

Setting the Fuze: The fuze is set by rotating the movable part of the fuze body (the scale) until the desired time indicator aligns with the fixed part of the fuze body (the index).

• Overall length: 10.16 cm
• Visible length: 7.62 cm
• Thread diameter: 51 mm
• Weight: 453 g
• Setting time range: 2 to 75 seconds

Fuze Installation:

The fuze is screwed into the main eye of the projectile and tightened with a wrench. Before firing, the safety pin must be removed. If the shot is fired with the safety pin still in place, the fuze will not initiate.

Setting for Time Action: The time setting is adjusted by rotating the time scale (in the direction indicated by the arrow on the fuze body) from 2 to 75 seconds until the desired index aligns with the mark on the body.

Setting for Impact Action: The fuze is set by turning the time scale (in the direction indicated by the arrow on the fuze body) from position “S” (service position, safe for use) to the first ungraduated mark. The fuze will also function in impact mode (initiate) if the time to target impact is shorter than the set time on the scale.

Caution:

Heavy rain may cause the fuze to initiate prematurely during firing.

When firing for timed (airburst) detonation with 155 mm guns, misfires may occur on charges 1 or 2 due to insufficient setback force to release the timing mechanism. In such cases, the fuze will default to impact action.

The M501/M501A1 fuze is not completely safe. Dropping or mishandling a projectile equipped with an M501/M501A1 fuze may lead to detonation and the detachment of individual components.

The safety pin must be removed immediately before firing.

The M520A1 (M520) fuze is a mechanical clock-type fuze with dual-purpose impact and time functions, used for 155 mm artillery shells.

The fuze can be used to achieve airburst (time action) or impact detonation of the projectile (fragmentation action).

• Length (with detonator): 12.7 cm
• Weight (with detonator): 907 g
• Fuze thread: 1-7-14NS-1
• Setting time range: 2 to 75 seconds
• Minimum rotation speed for arming: 2000 rpm

Fuze Installation:

The fuze is screwed into the main eye of the projectile and tightened using a wrench. Before firing, the safety pin must be removed. If fired with the safety pin still in place, the fuze will not initiate.

Setting for Time Action: Set the time by rotating the time-setting scale (in the direction indicated by the arrow on the fuze body), which is graduated from 0.5 to 75 seconds, until the desired numeric index aligns with the mark on the fuze body.

Setting for Impact Action: Set by rotating the time-setting scale (in the direction indicated by the arrow on the fuze body) from the position “S” (service position, safe use) to the first ungraduated mark. The fuze will also function in impact mode (initiate) if the time to target impact is shorter than the time set on the scale.

Differences Between M520 and M520A1 Fuzes:

• Delay Mechanism Activation: In the M520A1 fuze, the delay mechanism is activated at a distance of 60 m from the muzzle after firing, whereas in the M520 fuze, it is activated at 45 m.

Cautions:

• Heavy Rain: Firing during heavy rain may lead to premature fuze activation.
• Misfires on Time Setting with 155 mm Howitzers: When firing for timed bursts with 155 mm howitzers M1, M1A1, or M45, misfires may occur with charges 1 or 2 due to insufficient setback force to release the timing mechanism. In such cases, the fuze will switch to impact action.
• Removing Safety Pin: The safety pin must be removed immediately before firing.

Differences in Time Setting Between M564 and M520A1 Fuzes:

• From 2.0 to 2.2 seconds, the correction is 0.2 seconds.
• From 2.3 to 5.9 seconds, the correction is 0.3 seconds.
• From 6.0 to 9.7 seconds, the correction is 0.4 seconds.
• From 9.8 to 13.5 seconds, the correction is 0.5 seconds.
• From 13.6 to 17.3 seconds, the correction is 0.6 seconds.
• From 17.4 to 21.1 seconds, the correction is 0.7 seconds.
• From 21.2 to 24.9 seconds, the correction is 0.8 seconds.
• From 25.0 to 28.7 seconds, the correction is 0.9 seconds.
• From 28.8 to 32.5 seconds, the correction is 1.0 second.
• From 32.6 to 36.3 seconds, the correction is 1.1 seconds.
• From 36.4 to 40.1 seconds, the correction is 1.2 seconds.
• From 40.2 to 43.9 seconds, the correction is 1.3 seconds.
• From 44.0 to 47.7 seconds, the correction is 1.4 seconds.
• From 47.8 to 51.5 seconds, the correction is 1.5 seconds.
• From 51.6 to 55.3 seconds, the correction is 1.6 seconds.
• From 55.4 to 58.0 seconds, the correction is 1.7 seconds.

The M564 is an American high-explosive (HE), mechanically timed super-quick (MTSQ), clock-type fuze with dual-purpose impact and time functions, used for 105 mm and 155 mm artillery shells.

• Weight: 907 g
• Overall length: 12.7 cm
• Visible length: 7.62 cm
• Fuze thread: 212-UNS-1A
• Fuze arming distance after firing: 66 m from the muzzle

Fuze Installation:

The fuze is screwed into the main eye of the projectile and tightened using a wrench.

Setting for Time Action:

Set the fuze by rotating the time-setting scale (in the direction indicated by the arrow on the fuze body), which is graduated from 2 to 100 seconds, until the desired numeric index aligns with the mark on the body.

Setting for Impact Action:

If impact action (fragmentation action) is required, set the adjustment scale to the “90 seconds” position. The fuze will also initiate in impact mode if the time to impact is shorter than the time set on the scale. Additionally, if the timing mechanism is faulty, detonation will be initiated by the striker pin sharply moving towards the detonator cap upon impact, causing the detonator to initiate.

Cautions:

• Fuzes manufactured before January 1970 should be set to 90 seconds if only impact action is required.
• For fuzes produced from January 1970 onwards, if impact action is needed, they can be set to either “S” or “90 seconds.” However, current doctrine specifies that all M564 fuzes, regardless of production date, should be set to 90 seconds if impact action is required.
• Premature initiation may occur when firing in rain.
• To avoid accidental activation, do not drop, roll, or strike the fuze under any circumstances.

Differences in Time Setting Between M564 and M520A1 Fuzes:

• From 2.0 to 2.2 seconds, the correction is 0.2 seconds.
• From 2.3 to 5.9 seconds, the correction is 0.3 seconds.
• From 6.0 to 9.7 seconds, the correction is 0.4 seconds.
• From 9.8 to 13.5 seconds, the correction is 0.5 seconds.
• From 13.6 to 17.3 seconds, the correction is 0.6 seconds.
• From 17.4 to 21.1 seconds, the correction is 0.7 seconds.
• From 21.2 to 24.9 seconds, the correction is 0.8 seconds.
• From 25.0 to 28.7 seconds, the correction is 0.9 seconds.
• From 28.8 to 32.5 seconds, the correction is 1.0 second.
• From 32.6 to 36.3 seconds, the correction is 1.1 seconds.
• From 36.4 to 40.1 seconds, the correction is 1.2 seconds.
• From 40.2 to 43.9 seconds, the correction is 1.3 seconds.
• From 44.0 to 47.7 seconds, the correction is 1.4 seconds.
• From 47.8 to 51.5 seconds, the correction is 1.5 seconds.
• From 51.6 to 55.3 seconds, the correction is 1.6 seconds.
• From 55.4 to 58.0 seconds, the correction is 1.7 seconds.

The M565 is an American high-explosive (HE), mechanically timed (MT), clock-type fuze with dual-purpose impact and time functions, used for 105 mm and 203 mm artillery shells.

The M565 fuze is similar to the M564, except that it lacks the super-quick action, point detonating assembly, and auxiliary cap.

It can be set from 2 to 100 seconds and uses a vernier scale to provide 0.1-second accuracy.

• Weight: 930 g
• Overall length: 134.1 mm
• Visible length: 95.8 mm
• Fuze thread: 212-UNS-1A
• Temperature range: -40ºC to +52ºC
• Fuze arming distance after firing: 61 m from the muzzle

Fuze Installation:

The fuze is screwed into the main eye of the projectile and tightened using a wrench.

Setting for Time Action:

Set the time by rotating the time-setting scale (in the direction indicated by the arrow on the fuze body), which is graduated from 2 to 100 seconds, until the desired numeric index aligns with the mark on the fuze body.

Setting for Impact Action:

If impact action (fragmentation action) is required, set the adjustment scale to the “90 seconds” position. The fuze will also initiate in impact mode if the time to target impact is shorter than the time set on the scale. Additionally, if the timing mechanism is faulty, detonation will be initiated by the striker pin sharply moving towards the detonator cap upon impact, causing the detonator to initiate.

Cautions:

Fuzes manufactured before January 1970 should be set to 90 seconds if only impact action is required.

Fuzes produced from January 1970 onwards can be set to “S” or “90 seconds” for impact action. However, current doctrine requires all M565 fuzes, regardless of production date, to be set to 90 seconds for impact action.

Premature initiation may occur when firing in rain. To avoid accidental initiation, do not drop, roll, or strike the fuze under any circumstances.

The M577 series fuze is the same as the M582 series fuze, except that it contains a different detonating composition and cap.

The M582 fuze is a mechanical clock-type fuze with impact and time functions, used with 155 mm HE shells, M107; M549/M549A1 HERA; and both M110 Agent and WP Smoke.

The fuze contains a mechanical timing mechanism that can be set to operate at any time from 2 to 200 seconds.

• Weight: 454 g
• Overall length: 12.7 cm
• Visible length: 7.62 cm
• Setting time range: 2 to 200 seconds

Fuze Installation:

The fuze is screwed into the main eye of the projectile and tightened using a wrench.

Setting for Time Action:

The fuze is set using a setting key or a flathead screwdriver. The adjustment screw is located on the end of the upper part of the fuze, and the required time is displayed on three dials through a window on the side. The dial closest to the top indicates hundreds of seconds or a triangle for setting time, the second dial shows tens of seconds, and the third dial displays seconds and tenths of seconds.

If you need to decrease the detonation time on a fuze that was previously set for a longer time, turn clockwise (the numbers on the scale decrease) at least 1 second less than the desired setting (e.g., 24.5 for 25.5). Then change the direction to counterclockwise and set the required value opposite the index mark on the scale.

To return the setting to the transport and storage position, carefully turn clockwise until it stops between ◀ 93.5 and ◀ 95.5. After that, stop and do not apply extra force. 199.9 seconds is the maximum; 200 is not a supported setting by the manufacturer. The instructions prohibit turning it beyond 200 seconds or below ◀ 93.5.

You cannot set the time when the ◀ symbol is displayed; the fuze will not function properly in this state.

Setting for Impact Action:

If impact action (fragmentation action) is required, set the adjustment scale to position ◀ 98 for point detonation (fragmentation).

Cautions:

The fuze is considered unfit for use if it has been out of its standard container for more than 30 days.

For the “impact action” setting to function properly, a minimum projectile speed of 500 km/h upon collision is required.

The fuze may fail to function or detonate on impact if the set time to detonation is shorter than the time required for the fuze to arm.

For the first shot, reduce the time setting by 0.2 seconds to ensure an airburst. Then observe the dispersion pattern and adjust the burst height accordingly.

Note that if you decrease the time setting, the burst may occur short of the target.

The M732A2 is an advanced proximity fuze used in artillery shells for providing controlled detonation based on proximity to a target. It is a modern version designed to offer high reliability and multiple settings to ensure versatility in various battlefield scenarios.

Features:

• Type: Proximity fuze with additional impact functions
• Compatibility: Designed for use with high-explosive (HE) artillery shells, particularly for 105 mm and 155 mm caliber projectiles
• Modes of Operation: The M732A2 has selectable modes, allowing for proximity (variable time), time-based, or impact detonation
• Adjustable Setting: The proximity setting can be adjusted to achieve detonation at an optimal height above the target, increasing effectiveness against personnel or soft targets

Operation:

• Proximity Mode (Variable Time): Activates the fuze when the shell reaches a certain proximity to the ground or a target, creating an airburst for maximum fragmentation coverage.
• Impact Mode: If the proximity function fails or is turned off, the fuze acts as a point detonating (PD) fuze, initiating detonation upon impact.

Characteristics:

• Arming Distance: The fuze arms after traveling a safe distance from the muzzle, ensuring safe handling and transport.
• Settings and Activation: The M732A2 fuze can be set using a special setting tool or manually. The settings allow for precise adjustments based on mission requirements, either for airburst (height-based detonation) or impact action.
• Safety: Equipped with multiple safety mechanisms to prevent accidental initiation during handling, transport, or loading.

Applications:

• Use Cases: The M732A2 is suitable for scenarios that require airburst detonation to maximize area coverage against infantry and soft targets. It is also effective for direct hits where impact detonation is needed.
• Proximity Function: The proximity feature is especially valuable in anti-personnel roles, as it creates a shrapnel pattern effective over a large area, providing both offensive and defensive capabilities.

This fuze is often used in modern artillery systems due to its reliability and multiple functionalities, making it adaptable for different types of missions and target engagements.

• Color: Light brown, with a black tip
• Material: Metal body with a plastic tip
• Overall length: 14.7 cm
• Visible length: 9.55 cm
• Weight: 562 g
• Time setting range: 4 – 156 seconds, in 2-second increments
• Fuze activation after firing: Approximately 60 m
• Power source: Lithium battery, lifespan of 20 years

Fuze Installation:

The fuze is screwed into the main eye of the projectile and tightened using a wrench.

Setting for Time Action:

Press down the time-setting ring latch and rotate the sleeve (time-setting ring) to the desired value. Once the required value is set, release the latch.

Fuze Activation:

Activation of the fuze begins at the moment of firing, due to the forces of inertia, and completes as the projectile rotates approximately 60 m after leaving the barrel. At the same time, a glass ampoule containing the electrolyte is broken, and the rotation causes the electrolyte to spread within the battery, thereby activating both the battery and the fuze.

Proximity Mode:

In proximity mode, the sensor circuit is activated 2.8 seconds before the set time, and the sensor element initiates detonation of the projectile at a distance of 7 m above the target.

Impact Action:

If the proximity mode fails, the impact mode is activated.

Cautions:

A loaded projectile with the fuze installed must not be lifted by the fuze.

The fuze was developed as an upgrade of the M732 to ensure compatibility with Advanced Precision Systems (APS).

A fuze of German manufacture, mechanical clock-type with point detonation (PD). It is used with airburst projectiles (such as smoke and illumination) as well as high-explosive fragmentation munitions.

• Type: Mechanical, impact-time fuze
• Material: Metal body
• Overall length: 12.4 cm
• Visible length: 9.9 cm
• Diameter: 6.1 cm
• Thread diameter: 5.1 cm
• Weight: 670 g
• Time setting range: 2-150 seconds
• Fuze activation: 50 m after the projectile exits the barrel

Setting for Time Action:

The time setting is adjusted by rotating the central section, which is graduated from 2 to 150 seconds, until the desired numeric index aligns with the mark on the body.

Setting for Impact Action:

If impact action (fragmentation action) is required, the setting scale should be left in the initial position. The fuze will also function in impact mode if the time to impact is shorter than the time set on the scale. If the timing mechanism is faulty, detonation will be initiated by the striker pin moving sharply towards the detonator cap upon impact, causing the detonator to activate.

The B-90 is a mechanical fuze with a clock mechanism for high-explosive (HE) fragmentation shells. Shells equipped with the V-90 fuze are suitable for use against self-propelled and towed guns (mortars), lightly armored vehicles, openly positioned enemy personnel, and personnel in uncovered trenches.

Effective impact occurs at a burst height of 10-20 meters above the target. If the timing mechanism fails or if there is an error in setting the fuze in the increase direction, the fuze will detonate on impact (point detonating, PD).

The fuze is armed at a distance of 50 to 300 meters from the gun.

This fuze was originally developed in the USSR, but some manufacturers have adapted it to NATO standards by modifying the thread. There are examples of its use in the war between Ukraine and russia.

Setting Fuze V-90 to Proximity Action:

The total time for proximity action under stationary conditions is 90 seconds. Unscrew the hermetic cap with a wrench just before firing. The fuze can be set to proximity action using either key ZI36 or ZI37.

The ZI36 setting key has a scale ranging from 10 to 450, with 440 divisions.
In the absence of key ZI36, the setting can be performed with key ZI37, using the scale marked on the main sleeve of the fuze, which has 88 divisions.

Important Note for Firing in Rain:
Do not remove the setting cap during firing in rain to prevent premature detonations on the trajectory.

The fuze is described in Kropyv only for Soviet-style systems. To achieve an airburst with 155 mm guns, proceed as follows:

The fuze has a scale of 450 divisions, corresponding to 90 seconds until activation. Thus, each division represents 0.2 seconds. The effective average burst height is 15 meters above the target.

The activation time of the fuze is set to match the projectile’s flight time. Increase the sight by 10-15 thousand (e.g., milliradians). After the first shot, if a ground burst occurs, add another 10 thousand to the sight setting until an airburst is achieved.

In rain, use the fuze only with the cap on, which corresponds to high-explosive action in the case of impact with an obstacle. The timing mechanism will function as it does without the cap.