Bofors 40mm fuze types


Can anyone explain the difference between the 291 and the 295 fuze for the Bofors 40mm rounds please?

Is one direct action and the other a time fuze?

Kind regards,

Hi Andy,

you are sure that you means “291” and “295” and not “251” and “255”?
I found only a description about the “255”.

Hi Rob,

I was using the numbers that are stamped on the fuzes,so presumed that these were the model numbers.

The ‘259’ is a one piece fuze,while the ‘295’ is 3 piece.

They are both wartime dated if this helps.

Kind regards,

I guess it’s true, you’re never too old to learn something new. In my case, I had no idea that there was such a thing as 40mm Time Fuzed projectile. Or maybe I knew and simply forgot. My experience is limited to US Navy shipboard AA guns so I have to ask, how was the time fuze set?


Andy, can you show us some images please.

I would really wonder about a time fuze.

The only UK 40mm having a time fuze was the 2Pdr AA as far as I remember.

I’m positive that the 40mm Bofors AA round would have had a time fuze,wouldn’t it?

I actually have never heard of, not that it may not exist but that is why I would like to see some images of it.

I’m with EOD. I’d like to see some photographs. Not that i’m doubting their existance but all of the Bofors that I’m familiar with were clip or magazine fed and i can’t see how a time fuze would have been set prior to loading.

Is it possible that the one-piece fuze you referred to is an AP??


Not sure if this picture I found is helpfull? Is the sectioned 40 MM projectile (TOP CENTER) a time fuze?

Also, do all time fuzes need to be adjustible? If not, maybe the clips held rounds that all delayed at the same factory preset time? Totaly making this up thinking out loud. :-)



The sectioned projectile is the common AA HE I T, the same as the one on the sectioned case at the top. As regards having pre-set time fuzes, that would be a very impractical idea and not at all workable. JMHO


Thanks so much Ray! I am such a novice :-) haha! Duh.

Fuzes of all types are pretty spectacular. It is amazing how much goes into some of the more complex ones. Those diagrams are great Ray!

Yes, that’s why they called time fuze. They are intended to set of the shell on the designated point of the trajectory.

Fixed time detonating is usually an additional feature in impact fuzes to prevent the shell from fallback and hit own forces. It can be done by pyrotechnical or mechanical way. Another way for the self destruction is by the burnout of the tracer element.



You’re correct. The sectioned projectile in the photo by Jason is a Self-Destruct (SD) as can be seen by the vent leading from the tracer to the TNT pellet.

I do need to correct something I said previously. The sectioned projectile is an HE I T but the one on the sectioned case is an HE T.


I also didn’t found anything about 291 and 295, but here is the drwing of the No.255


Thanks for clarifying things Ray! I like the ID tip of identifying the channel between tracer and tnt as a self destruct design. Totally did not know that.

None of the fuzes for the US 40mm ammo of WW2 and later were “time” fuzes. All were impact or impact with self destroying feature. Germany,japane,Hungary,England and others used the guns and I have never seen any “time” fuze development prior to the Sgt. York program when a prox. fuze was developed.

A time fuze for such a small shell is a waste of time due to a variety of factors. Unacceptable kill rate being the top.

The proximity (or variable time fuze as it was called during the WW2 era) is more practical BUT still did not produce sufficient kill rates with the York system to warrant adoption.

We still use the 40 L60 Bofors on the c130 gun ships but not with time fuzes.

The biggest problem with time fuzes and AA is, of course, in setting the fuze. Without the development of proximity fuzes, guns such as the 3"/50 Rapid Fire would not have been successful. Even the well known 5"/38 and later 5"/54 guns were only marginally effective with MT fuzed projectiles when used as AA batteries.


Small caliber shells with time fuzes were used as said before but the effect might have been marginal.

The existing typese where as said the 40mm 2Pdr Vickers (UK and Japanese service) and the German 5cm Flak 41, the Russian Navy even used such fuzes on 37mm Hotchkiss (actually they adapted the British design).
The fuze setting was done in all types by a sprocket type setting wheel on the fuze body which was turned on feeding of the cartridge. The “length of the turn” was set by a “bar with teeth” the fuze was passing. So the bar was extended or shortened by swinging in or out the qty of teeth.

As everybody said before no such system is known (so far) for the 40x311R 40/L60 Bofors.