German WW2 75mm rnd with 37mm FlaK fuze


I have a German WW2 7.5cm round that is a bit of a mystery.

It doesn’t have the usual fuze associated with this round,but has what looks like an unmarked 3.7cm flak fuze which screws into an adaptor,then into the top of the projectile.
The base of the adaptor is threaded on the inside for a booster charge maybe?

I have been informed that if this is a 3.7cm fuze when the round was fired the fuze wouldn’t arm so the projectile wouldn’t explode,I thought that is maybe why the adaptor has a thread,possibly for a booster charge,but have also been informed that even if it did have a booster charge that the fuze still wouldn’t arm.
So,what do I have here?
Is it an experimental round,or a case of using what was available at the end of the war?
Or,has a collector manufactured the adaptor and stuck a 3.7cm fuze on until he can get the correct fuze?

All help appreciated with this as I’m stumped!
Kind regards,






I don’t know the answers to all your questions but maybe my comments will help.

An adapter (also called a head) was usually intended soley as a means to attach a fuze to the projectile. It allowed for a bigger opening in the projectile itself which, in turn, made machining and loading of the projectile much easier. Booster charges were generally attached to the fuze and not the adapter.

Many high capacity (HC), and some armor or concrete piercing projectiles had the booster or an auxiliary detonating fuse attached to the adaptor rather than the fuse and that may be what you have, possibly with an incorrect fuze?

Why an adapter would prevent the fuze from arming I haven’t a clue. The arming mechanism is in the fuze itself. It may be that what your source meant was that a projectile with an auxiliary detonating (AUX DET) fuse attached to the adaptor acts as a safety device to prevent the projectile from bursting in the event of premature arming of the noze fuse or damge to the fuze itself.

But, the Germans did some strange things when it came to ordnance and I suppose anything is possible.




Many thanks for your reply,much appreciated!

The guy who told me the info about the projectile and fuze said that if it was a 3.7cm fuze it wouldn’t arm as the 3.7cm round has a higher setback(whatever this means!) and also there wouldn’t be enough force for it to arm,(something about different gravity forces/insufficient forces).

The fuze has also been described as an unusual example of a 3.7cm fuze.

It fits my 3.7cm round and also the fuze from my 3.7 fits into the adaptor.

He also mentioned that the projectile is slightly rebated above the driving band,which he found unusual and couldn’t give an explanation for.

Also suggested was that it was a round for the Geb 36 mountain gun due to the filling code stamped on the projectile,although this has been discounted as apparently the driving band is too large for it to be this round.

The mystery deepens!!

Kind regards,



“Setback” is one method by which a fuze is armed. Basically it’s the force of inertia which tends to move all fuze parts to the rear as the projectile is accelerated in the bore of the gun. Another method is by centrifigal force, caused by the rotation of the projectile in flight, which tends to move all fuze parts radially away from the axis of the projectile. Apparantly the 3.7cm fuze requires unusually high forces.

The recess above the rotating band is unusual. It is possibly a feature resulting from how the band itself is installed during manufacture of the projectille ??

Unfortunately, there exists a lot of big ordnance that has been put together from parts from here and and parts from there. I have a couple of these myself. They make good display pieces even if not technically correct. I’m not saying that you have one of them, just a possibility.



Thanks again Ray!

The one thing I can do is to obtain the correct fuze and put it on,making it a correct example (apart from the slight recess above the band) of a Pak or KwK 40 round.

Kind regards,


Sometimes hard to tell things from a photo. In some images the fuze looks to be aluminum and in others steel. Which is it ? Can you unscrew the base of the fuze and photo the interior ? The condition of the surface of the adaptor implies that it did not belong to this shell. This does not mean that it did not go to this TYPE of shell. However the condition of it is inconsistent , given the surface pocking , with the projectile body proper. There is no good reason that such an adaptor could not be used to save money on such an HE shell by using a cheaper and less complicated fuze. The “set back” arming should not be a problem. As this appears NOT to be a standard nose fuze for 37mm ammo the parameters of function are ,from this available information ,unknowable. I would like to see the inside of the fuze.


The fuze is aluminium (non-magnetic),the adaptor is steel.

Unfortunately, I can’t get into the fuze,I’ve tried and it won’t move!
The adaptor isn’t ‘pocked’, it has a coating of black paint on it,almost like a crackle type finish.

Kind regards,


Managed to unscrew the base.

Looks to me to be just the same as any other 3.7cm fuze,clockwork!

Kind regards,


Photo? I have passed this info on the Jim O’Brien who is the world’s expert on such things. He is looking into it.


Photo will have to wait unti I can pluck up the courage to open it again!

Once openes all the insides fell out,took ages to get it all back in!

Kind regards,