Fusing on Bofors rounds

[brand]

Hi all,

I have had a nagging, but probably dumb question on the fusing of WW2 bofors rounds.

These were presumably designed to blow on impact with an aircraft, and I think, timed to blow up afterwards. I had it in my mind that it would be ideal to set them to blow only shortly beyond the intended target. By which, I imagine firing at an aircraft which is 3000 yards away, and having the rounds blow after say 4000 yards, as a deterrant to following planes.

Was this how they worked? Was it even possible to change fuse settings when firing at such a rapid rate ?

regards Brand

 

[radioman1]

Info on Naval 40/ 60 Rounds

1 fitted with a N259 contact fuze also a 12 sec tracer ignitor so if it missed the target it would explode
2 As far as i know the 259 was not a proximity fuze
3 So its not possible as a 259 was a DA (Direct Action) fuze

Hope this info helps

regards Steve

 

[ozziammo]

Howdy Brand,

I think you will find that nothing was designed as a deterrent, as the aircrew knew what they are in for.

The self destruct component of an artillery projectile is designed so that if the target was missed then it would self destruct so as not to allow un-exploded projectiles to land back to earth, a) so that friendly ground would not be subjected to their own HE shell falling on them, b) so that there were no UXO problems after the event.

Regards Ozzi.

 

[Darkman]

Hi Brand,

As far as I am aware all of the Bofors fuzes No's 250, 251, 255, 259 right through to No. 306 were simple Direct Action contact fuzes and as such had no (need for) setting capability. I'm not saying that proximity fuzes were not possibly developed or used, but the very recent (1980s -1990s) No. 306 fuse is still a simple DA fuze. As mentioned by others, they had a "self destruct" facility after the tracer compound had expended.

Cheers,

Graeme

 

[lcn]

Hi Steve
We begin to find Time fuses from 3 inch (No199) and from 3.7 inch there were mechanical time fuzes (series of No200 fuzes) and later fuzes VT (T98 - 3.7 inch AA).
These fuzes allowed to run the shell on the trajectory or near the target.
The shells of 40 mm Bofors was too small to receive these fuzes
A question for Darkman
I do not the fuze No306 is it be possible to more information please
Cordialement
Jean Paul

 

[Tony Williams]

I believe that proximity fuzes for the 40mm Bofors were not fielded until the 1970s.

The current state-of-the-art fuze they use is the 3P (used on both 40mm and 57mm) which combines various different proximity, time and impact functions, settable as required.

As a side note: the 2-pr naval pom-pom originally used settable times fuzes for the AA role, by by WW2 these were being replaced by impact fuzes.

Also, when it comes to deterrents, the best one was a big, bright tracer. In the 1941 naval action in which the Repulse and Prince of Wales were sunk, it was noted that the 40mm Bofors, firing tracer ammo, would cause attacking torpedo bombers to veer off course, but the 2-pr, which had no tracer, lacked this effect.

 

[Darkman]

Bofors L60 No. 306 fuze

Jean Paul,

The Australian Navy used No.306 DA fuzes on L60 Bofors 40mm rounds from at least the 1980s possibly through to until they became obsolete as recently as 2007. The 1985 Navy fuze in the attached images belongs to a friend and is on a complete round with the case dated 1993. "MF" is for the Munitions factory at Footscray, Melbourne.

Cheers,

Graeme

Hi Steve
We begin to find Time fuses from 3 inch (No199) and from 3.7 inch there were mechanical time fuzes (series of No200 fuzes) and later fuzes VT (T98 - 3.7 inch AA).
These fuzes allowed to run the shell on the trajectory or near the target.
The shells of 40 mm Bofors was too small to receive these fuzes
A question for Darkman
I do not the fuze No306 is it be possible to more information please
Cordialement
Jean Paul

 

[brand]

Thanks for all the replies chaps.

A 12 second timed fuse, means the round will safely detonate at around 10,000m from the gun.

It seems fairly unlikey to hit a moving aircraft at say 3000m. This is why it made sense to me to have the rounds self destruct just a little beyond this. As the plane approaches, you open up when it it just over 4000m away, and show it a wall of explosions that it has to fly through.

I had not taken into account that the tracer in the round, may have a similar if not more effective result. I suppose also that a cloud of explosions around or behind the target may interfer with the visability of actually shooting at it.

Thanks.

 

[radioman1]

1 Its the 12 second tracer ignitor that detonates the round not the fuze if it does not hit the target
2 Did exchange 259 fitted rounds with a fuze from Bofors cant remember the number or mark

Regards Steve

 

[Quatermass]

Tracer and Igniter Shell No.11, mean time to self-destruction 6 1/4-seconds

Tracer and Igniter Shell No.12, mean time to self-destruction 6 1/4-seconds

Tracer and Igniter Shell No.14, mean time to self-destruction 12-seconds

Action of the Tracer and Igniter Shell No.11: On firing, the propellant explosion forces in the closing cap and ignites the priming compostion, which in turn ignites the tracer composition. Should the shell not function by D.A., the tracer composition burns through to the gunpowder, the later is ignited and the shell filling exploded.

 

[orcutteod]

Enclosed are pictures of an USN WWII era 40mm Bofors fuse that my father gave me years ago.

 

[bacarnal]

One thing that I had learned recently about the 40mm Bofors and the 37mm after calling it "self destruct for years" (at least in US parlance) is the the SD does not mean that, but means, "shell destroying". For the US versions of the 40mm Bofors, the M54 HE shell for the aircraft and the AA canon, there was a wafer of black powder weighing about 32 to 55 grains (depending on shell) which would cause the shell to destroy after the tracer burned through. Still don't know if the black pwder charge would cause the HE to detonate within the confined space, or caused the shell to break up. This is not to say that when SD is applied other nomenclature, it doesn't mean self destruct, just in relation to US 40mm and 37mm. I know it's semantics, but that's what is in the pubs. Cheers, Y'all, Bruce.