Fuze M51A5

Contents

Fuze M51A5

M51A5 A1, A2 (M51) Impact Fuze

Point-detonating fuze M51A5 is a selectable fuze with super-quick action or a 0.05-second delay, designed to detonate high-explosive munitions of 75 to 105 mm caliber.

The M51A5 fuze consists of the M48A3 fuze combined with the M21A4 booster. The head of the fuze contains a firing pin held in position by a support that prevents activation of the M24 detonator until impact. The fuze body includes the M1 delay plunger assembly and an interrupter assembly with a setting sleeve, which allows setting or selecting either the super-quick (PD) mode or the delay function.

 

M51A5 parts

 

The delay plunger consists of a striker and the M2 delay element, which includes the M54 primer, a black powder delay charge and the M7 relay. The head of the fuze is attached to the body by a flash tube, which also holds the windshield or ogive.

The ogive is a thin-walled stamped steel part that gives the fuze its aerodynamic shape. The M21A4 booster consists of a brass body with an external thread (2 inches, 12 threads per inch) for installation in projectiles and an internal thread (1.7 inches, 14 threads per inch) for attaching the fuzes.

The aluminum cup of the booster contains a 340-grain tetryl pellet attached to the booster body. The internal configuration of the M21A4 booster consists of an eccentric rotor that holds the M17 detonator in the unarmed position by means of centrifugal and return locks. When the locks release, the rotor aligns with the fuze charge and the flash tube if set to the super-quick (PD) mode, or with the delay plunger charge if set to delayed action.

 

Technical specifications

Tabular specifications:

  • Type: impact (PD)
  • Weight: 0.96 kg
  • Length:
    • Visible part: 95 mm
    • Overall: 151 mm

Temperature limits:

During firing:

  • Lower limit: -40°C
  • Upper limit: +51.7°C

For storage:

  • Lower limit: -62°C (no more than 3 days)
  • Upper limit: +71°C (no more than 24 hours)

Explosive components:

Super-quick mode (SQ):

  • M24 detonator, M17 detonator, main tetryl charge, tetryl booster charge.

Delay mode:

  • M1 delay plunger assembly (M2 delay element, M54 primer, black powder delay charge, M7 relay), M17 detonator, main tetryl charge, tetryl booster charge.

Warnings:

 Premature functioning. (Explained in "Usage notes")

 

Usage notes

Recommended for prohibition of use:

Munition designation: Fuze M51A5

  1. Lot: LOT SHX 3-24, LOT JHE 1-4
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 24.07.2024, No. 785/11/691/dsk
    Decision: Prohibit

  2. Lot: LOT SXH 3-25, LOT E-FBO-1-35
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 01.08.2024, № 370/3076
    Decision: Prohibit

  3. Lot: LOT KF MKE-231-5-1989, LOT KF MKE 200-8-1985, LOT KF MKE 209-6-86, LOT SXH-12-9-55, LOT HXP 94455, LOT KF MKE-225, LOT SHX 3-24, LOT SXG 3-24
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 12.08.2024, No. 370/3202/dsk
    Decision: Prohibit

  4. Munition designation: Fuze MRV-U
    Lot: PDAZ-127 9153/1518
    Reason: Faulty rocket-assist component 
    Date of order: 30.08.2024, No. 370/3510/dsk
    Decision: Prohibit

  5. Lot: KF MKE 234-1-1990
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 10.09.2024, No. 370/3644/dsk
    Decision: Prohibit

  6. Lot: KF MKE 229 10-1988, KF MKE 230 1-1989, KF E-FBO-1-38-11-56
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 13.09.2024, No. 370/3712/dsk
    Decision: Prohibit

  7. Lot: 05-SFC
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 22.09.2024, No. 370/3858/dsk
    Decision: Prohibit

  8. Lot: JA-502-202 4-51
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 23.09.2024, No. 370/3880/dsk
    Decision: Prohibit

  9. Lot: MKE-217
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 25.09.2024, No. 370/3912/dsk
    Decision: Prohibit

  10. Lot: WVZ-2-5-7-55
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 17.10.2024, No. 370/4594/dsk
    Decision: Prohibit

  11. Lot: PRD 11-19-3-56
    Reason: Projectile bursts on leaving the barrel bore
    Date of order: 23.10.2024, No. 370/4503/dsk
    Decision: Prohibit

 

Fuze Setting

The fuze is screwed into the fuze socket of the projectile and tightened with a wrench.

To set the fuze:

  • - for impact action, use the wrench or a flat screwdriver to turn the plunger slot to the “SQ” position. (the position SQ – Super Quick) is the default position. Check that the fuze indicator points to SQ);
  • - for impact action with delay: use the wrench or a flat screwdriver to turn the plunger slot to the “DELAY” position.

 

 

Oleh Syrota (Georgich©) for the Armed Forces of Ukraine / Entropia.com.ua

  

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