What's new
British Ordnance Collectors Network

This is a sample guest message. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

40mm Bofors fuzes.

BMG50

BMG50

Well-Known Member
Premium Member
I know that the 3.7 AA projectiles have time fuzes and explode at a given height but how does 40mm Bofors fuzes work, seems to be no clock work mechanism for them. Were impact fuzes used? If so, you would have to be a bloody good shot to hit an aircraft high up. What happens to the ones that miss, quite a large round to have a self destruct fuze and it explodes hitting the ground.
 
Can’t download the files. Did 40mm Bofors use clockwork fuzes or is this 3.7 fuzes shown.
 
BMG50 said:
Can’t download the files. Did 40mm Bofors use clockwork fuzes or is this 3.7 fuzes shown.
Click to expand...

My bad. It's for the 3.7. I'll keep digging.

Update: Your conclusion there was no timed/VT type fuze for the 40MM Bofors seems to be correct.
 
Last edited:
The U.S. WWII Bofors fuzes were impact. The AAA projectiles had a self-destroying tracer that would destroy the projectile after it burned through to the filler.
 
The 208 fuze has a mechanism with a run time of 43 seconds, then if it has not hit anything it functions, the same with the fuze 214. Both are for 3.7 Mks 1 - 3 gun. They are for shell with a 2" fuze hole.
British 40mm Bofors took the fuzes 251 or 255. These are 1.2" (1.196") fuze hole and have a Tracer and Igniter Shell No 11 (6.5 seconds to self destruct), Tracer and Igniter No 12 (also 6.5 seconds) or a Tracer Igniter Shell No 14 (12 seconds to self destruct), if they have not hit a target.
 
British 40mm Bofors rounds were fitted with percussion fuze No's 250, 251 and 255 during WW2 and No. 259 post war. In Australia we also developed and used the No. 306 fuze in the early 1970s through until the early 1990s.
 
Thanks guys for the information. I assume that there was a table for aircraft heights and timing of fuzed ammunition. First you had to be a good shot. Second you didn’t want your rounds exploding before it reached the target and so on, what height would 6.5 seconds give roughly. Rounds bursting around an aircraft would put it of its course on a bomb run but saying this the Bofors was quite a fast firing gun with tracer that would mark its target very quickly.
 
Each 3.7" battery was controlled by a predictor, which gave a predicted elevation and azimuth for the guns. Each gun had a machine fuze setter, which was synchronised with the constantly changing predictions, the fuze was offered up to the setter, which set the time, then the round was put in the gun for firing.
The first of these predictors used by the British was designed and made by Vickers soon after WWI, but by 1942 a US produced predictor, made by Sperry Gyroscopes was being used.
 
Last edited:
The timer function on the Bofors tracer and igniter was purely for self destruct purposes to avoid rounds that missed the target falling on friendlies. The fuze was an impact fuze only. The intention was to hit the target, unlike the 3.7" and similar where the intention was to burst the shell nearby.
 
So if a Bofors round missed it would burst higher up beyond the target, seen on the Kamikaze footage of ships being attacked when they send barrages on mass.
 
Yes if a Bofors projectile missed it would explode somewhere in trajectory beyond the target - assuming the target was at relatively low level - as light AA was intended. Movies depicting low level aircraft attacks with AA puffs bursting around the planes is completely inaccurate and purely for Hollywood effects. Heavy AA projectiles timed to explode in proximity to aircraft was for higher level attacks, e.g. bombers at 30,000 feet. They contained a smoke box to produce a visual smoke puff to aid ranging. I'm not sure what the lowest level these rounds could be set to explode, but it wouldn't be very low for safety. Someone else may know. I imagine that Kamikaze planes etc in formation could be attacked with heavy AA before they started their dives but not as they approached the ships.
 
Last edited:
Is there a TM manual showing the protocol of using Bofors in a AA role, do's and don'ts.
 
Some years ago I found a reference on the internet that AA shell fitted with non VT (proximity) fuzes had a hit rate of one in 8,000. Even with VT fuzes the hit rate increased only tenfold.
 
You must log in or register to reply here.
Top