Fuze M520A1 (M520)
Contents
M520A1 (M520) – mechanical time fuze with impact action
Fuze M520A1 (M520) – a mechanical time fuze with dual-purpose impact and remote (time) action, used for 155 mm artillery projectiles
The fuze can be used to achieve an air burst (remote action) or impact detonation of the projectile (fragmentation action).
Technical specifications
- length (with detonator): - 12.7 cm;
- weight (with detonator): - 907 g;
- fuze thread: - 1-7-14NS-1;
- time setting: - from 2 to 75 s;
- lowest rotation rate for arming: - 2,000 rpm.
Usage notes
Difference between the M520 and M520A1 fuze types:
The delay mechanism in the M520A1 fuze functions at a distance of 60 m from the muzzle after firing, and in the M520 fuze at a distance of 45 m.
Warnings:
Firing in heavy rain may cause premature functioning of the fuze.
When firing air bursts from 155 mm M1, M1A1 or M45 howitzers, misfires may occur on charge 1 or 2 because of insufficient inertia force to release the timing mechanism. In that case, however, the fuze will function on impact.
The safety pin must be removed immediately before firing.
Difference in the remote-fuze settings M564 and M520A1
| M564 | M520 – increment correction |
| from | to |
| 2.0 | 2.2 | 0.2 |
| 2.3 | 5.9 | 0.3 |
| 6.0 | 9.7 | 0.4 |
| 9.8 | 13.5 | 0.5 |
| 13.6 | 17.3 | 0.6 |
| 17.4 | 21.1 | 0.7 |
| 21.2 | 24.9 | 0.8 |
| 25.0 | 28.7 | 0.9 |
| 28.8 | 32.5 | 1.0 |
| 32.6 | 33.3 | 1.1 |
| 36.4 | 40.1 | 1.2 |
| 40.2 | 43.9 | 1.3 |
| 44.0 | 47.7 | 1.4 |
| 47.8 | 51.5 | 1.5 |
| 51.6 | 55.3 | 1.6 |
| 55.4 | 58.0 | 1.7 |
Fuze Setting
Setting the fuze:
The fuze is screwed into the fuze socket of the projectile and tightened with a wrench. The safety pin must be removed before firing. If the round is fired with the safety pin in place, the fuze will not be initiated.
Setting for remote (time) action:
It is set by turning the time-setting scale (in the direction indicated by the arrow on the fuze body), graduated from 0.5 to 75 seconds, until the required numerical index coincides with the mark on the body.
Setting for impact action:
It is set by turning the time-setting scale (in the direction indicated by the arrow on the fuze body) from the S position (service position, safe handling) to the first ungraduated mark.
The fuze will also function on impact (the fuze will be initiated) if its time to meeting an obstacle is less than the time set on the setting scale.
Oleh Syrota (Georgich©) for the Armed Forces of Ukraine / Entropia.com.ua
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