WW2 VT Fuzes

[Depotman]

I'm researching the US made VT (proximity) fuzes which were supplied to the UK in WW2. The only book I know of is 'The Secret Fuze' by Baldwin; and most of the British manuals post WW2 don't mention the fuzes or have any photos or detailed drawings.

Baldwin's book has tables of fuze production for both US and UK Army and Navy, but there are a couple of anomalies I would like some help with. I have attached two pages, 213 & 214 which show, on page 214, the problem.

The number of fuzes produced are sometimes split and I don't understand what the nomenclature means; for example:

British Army
T97 (Brit. Sm. How.)
T97 (Brit. Sm. How. RB6)

The T97 fuze was supplied for the 25-pdr (Brit. Sm. How.), but I don't understand what the 'RB6' version was, with a different number of fuzes produced for it. Very similar for the US Army with three different versions; T76 (Lg. How.), T76 (Lg. How. RB6), and T76 (Lg. How. RB12).


British Army
T98 (Brit. 3.7" AA)
T149 (Brit. 3.7" AA Short RD)

So, my two questions:

What did RB6 and RB12 mean?

What was the 3.7" AA Short RD?

Depotman

 

[Eggburt1969]

The RB abbreviation could possibly be short for 'Radio Band' or 'Radar band', and hence the frequency the fuze operated on.

 

[AE501]

The 3.7" short round refers to Ordnance QF 3.7" Mks 1 - 3 gun round, which used the T98 and T 149 fuzes, and various other fuzes.
The 3.7" long round refers is the Ordnance QF 3.7" Mk 6 gun round, which was considerably longer than the Mks 1 - 3 gun round, and only ever used Fuze No. 208 Marks 1 - 4, 5 and 6.
It is possible that RD refers to the Reduced Charge round applicable to the 3.7" Mks 1 - 3 gun.

There is some information in User Handbook Anti-Aircraft Ammunition 1949 which is in downloads.

 

[Eggburt1969]

Sorry, missed the stuff other than RB.

I don't think RD would be reduced charge in this instance, mainly as the T98 (later M94) and T149 (M95) aren't mean for ground-to-ground use and this is when the reduced charge would be used. For note, neither are meant for use with the Mk. 6 3.7" gun.

I'm guessing RD is just a typo and should be SD. This as there's also a T152 (90-mm AA Short SD), the 'Short SD' presumably meaning 'short self-destruct'. This compared with the standard time period taken for the SD system to function.

The aforementioned 1949 UK publication 'Anti-Aircraft Ammunition User Handbook' states that the T149 (M95) prox fuze has a mean SD time period of 10 seconds compared with 30 seconds for the T98 (M94).

The T97 (M98) can be used the 3.7" Mk. 1-3 guns when ground-to-ground targets are to be engaged.

 

[Depotman]

The 3.7" short round refers to Ordnance QF 3.7" Mks 1 - 3 gun round, which used the T98 and T 149 fuzes, and various other fuzes.
The 3.7" long round refers is the Ordnance QF 3.7" Mk 6 gun round, which was considerably longer than the Mks 1 - 3 gun round, and only ever used Fuze No. 208 Marks 1 - 4, 5 and 6.
It is possible that RD refers to the Reduced Charge round applicable to the 3.7" Mks 1 - 3 gun.

There is some information in User Handbook Anti-Aircraft Ammunition 1949 which is in downloads.

Thanks for the info; I've got a copy of the !949 Handbook on Anti-Aircraft Ammunition and the tables at the back of the book specify the T97, T98 and T149 fuzes for the 3.7" Mks. 1-3 and NO VT fuzes for the 3.7" Mk 6. The quantities produced for both the long and short 3.7" gun rounds in the 'Secret Fuze' book, bears no resemblance to the info in the 1949 book. I think the research I'm doing will be a challenge! Depotman

 

[Depotman]

Sorry, missed the stuff other than RB.

I don't think RD would be reduced charge in this instance, mainly as the T98 (later M94) and T149 (M95) aren't mean for ground-to-ground use and this is when the reduced charge would be used. For note, neither are meant for use with the Mk. 6 3.7" gun.

I'm guessing RD is just a typo and should be SD. This as there's also a T152 (90-mm AA Short SD), the 'Short SD' presumably meaning 'short self-destruct'. This compared with the standard time period taken for the SD system to function.

The aforementioned 1949 UK publication 'Anti-Aircraft Ammunition User Handbook' states that the T149 (M95) prox fuze has a mean SD time period of 10 seconds compared with 30 seconds for the T98 (M94).

The T97 (M98) can be used the 3.7" Mk. 1-3 guns when ground-to-ground targets are to be engaged.

Thanks for your replies; I'm still confused when comparing the info between the US and the British books. The short 3.7" has all three fuzes listed against it in the 1949 British book, but the US info implies that the T98 is for the long 3.7". The long 3.7" doesn't have any VT fuzes listed against it in the British 1949 book. My research still has some way to go! Depotman.

 

[Eggburt1969]

The US book doesn't have the long 3.7-inch Mk. 6 against any fuzes, as stated the 'Short RD' is likely 'Short SD', so it has a short self destruct (SD) time period, as per the T152 used with the US 90 mm. As far as I can tell it has nothing to do with the long 3.7-inch Mk. 6 gun.

Going by the UK book, the T98 and T149 as essentially the same, only differing in the SD time periods each has. The T97 is a slightly different design intended for ground-to-ground use with reduced charges.

As both the US and UK books do not list any fuzes against the long 3.7-inch Mk. 6 gun, there is no discrepancy.

The UK book also states on page 34 (46 in the PDF) and about VT fuzes, that (as of 1949) ...

5.236 Service Fuzes
Fuzes now in the service were all made in the United States and the only British A.A. gun for which they are approved is the 3.7-inch Marks 1 to 3.

So again, no discrepancy.

I would imagine there are no VT fuzes for the 3.7-inch Mk. 6 as there were, at that time, no projectiles with the suitable internal construction that could use the deep intrusion fuze. If you look at Appendix H ' Method of Filling' in the UK book, there's only one HE-filled shell for the 3.7-inch Mk. 6 gun and that's not constructed for use with VT fuzes.

So again, no discrepancy.

 

[Depotman]

The US book doesn't have the long 3.7-inch Mk. 6 against any fuzes, as stated the 'Short RD' is likely 'Short SD', so it has a short self destruct (SD) time period, as per the T152 used with the US 90 mm. As far as I can tell it has nothing to do with the long 3.7-inch Mk. 6 gun.

Going by the UK book, the T98 and T149 as essentially the same, only differing in the SD time periods each has. The T97 is a slightly different design intended for ground-to-ground use with reduced charges.

As both the US and UK books do not list any fuzes against the long 3.7-inch Mk. 6 gun, there is no discrepancy.

The UK book also states on page 34 (46 in the PDF) and about VT fuzes, that (as of 1949) ...

5.236 Service Fuzes
Fuzes now in the service were all made in the United States and the only British A.A. gun for which they are approved is the 3.7-inch Marks 1 to 3.

So again, no discrepancy.

I would imagine there are no VT fuzes for the 3.7-inch Mk. 6 as there were, at that time, no projectiles with the suitable internal construction that could use the deep intrusion fuze. If you look at Appendix H ' Method of Filling' in the UK book, there's only one HE-filled shell for the 3.7-inch Mk. 6 gun and that's not constructed for use with VT fuzes.

So again, no discrepancy.

Many thanks for your info and comments - US abbreviations were often different from UK and can cause confusion!

I haven't seen any UK references to the VT fuzes supplied for the Royal Navy - MK33, MK41, MK56 and MK 60. Have you any UK info on these?

Depotman

 

[Eggburt1969]

Actually I missed that there was one HE shell for the 3.7-inch Mk. 6 gun listed in the UK book on anti-aircraft ammunition that was for VT fuzes. This was the Mk. 4/1, its details listed in 'Appendix G' (page 69), but unfortunately no fuze was actually listed against it.

As to the MK 33, MK 41, MK 56 and MK 60 prox. fuzes, this is all I could find locally.

MK 33 = no details
MK 41 = RF proximity fuze for UK 4-in and 4.7-in guns
MK 56 = RF proximity fuze for UK 4.5-in and 5.25-in guns
MK 60 = no details

There is some data about some of the fuzes here.

https://www.si.edu/object/nasm_A19940233000

Neil

 

[Depotman]

Actually I missed that there was one HE shell for the 3.7-inch Mk. 6 gun listed in the UK book on anti-aircraft ammunition that was for VT fuzes. This was the Mk. 4/1, its details listed in 'Appendix G' (page 69), but unfortunately no fuze was actually listed against it.

As to the MK 33, MK 41, MK 56 and MK 60 prox. fuzes, this is all I could find locally.

MK 33 = no details
MK 41 = RF proximity fuze for UK 4-in and 4.7-in guns
MK 56 = RF proximity fuze for UK 4.5-in and 5.25-in guns
MK 60 = no details

There is some data about some of the fuzes here.

https://www.si.edu/object/nasm_A19940233000

Neil

Thanks Neil, you must have scoured the 1949 AA Ammo book to find the 3.7-in Mk 6 Shell Mk 4/1 for the VT fuze - took me ages!

I'd gone through br.932 (1945) online, for Naval VT fuzes without any 'hits'; until I checked my own copy which has many 'additions' pasted in. I found a table that listed the 4.5-in, 4.7-in Mk 11, and 5.25-in for the Mk 56 VT fuze; and the 4-in Mks 16* & 21, and 4.7-in Mks 9 & 12 for the Mk 60 VT fuze.

Where did you find your info on the Mk 41 fuze?

Your link has some excellent info that I'm still trawling through - much appreciated. Trevor

 

[Eggburt1969]

Thanks Neil, you must have scoured the 1949 AA Ammo book to find the 3.7-in Mk 6 Shell Mk 4/1 for the VT fuze - took me ages!

I'd gone through br.932 (1945) online, for Naval VT fuzes without any 'hits'; until I checked my own copy which has many 'additions' pasted in. I found a table that listed the 4.5-in, 4.7-in Mk 11, and 5.25-in for the Mk 56 VT fuze; and the 4-in Mks 16* & 21, and 4.7-in Mks 9 & 12 for the Mk 60 VT fuze.

Where did you find your info on the Mk 41 fuze?

Your link has some excellent info that I'm still trawling through - much appreciated. Trevor

Trevor,

I just happened upon it when looking for something else. As always with these sort of things, after my initial reply.

I checked my copy of BR 932 first of all, but unfortunately it's the scan floating around the web, and as such missing most its pages.

The additional data comes from various US Military (MIL) handbooks (HDBK), such as 137, 145 and 146.

If you can find the 1959 publication 'Army, Navy, Air Force, Fuze Catalog' and its first supplement by Gunther Cohn, that might help you too.

Neil

 

[Depotman]

Trevor,

I just happened upon it when looking for something else. As always with these sort of things, after my initial reply.

I checked my copy of BR 932 first of all, but unfortunately its the scan floating around the web, and as such missing most of the pages.

The additional data comes from various US Military (MIL) handbooks (HDBK), such as 137, 145 and 146.

If you can find the 1959 publication 'Army, Navy, Air Force, Fuze Catalog' and its first supplement by Gunther Cohn, that might help you too.

Neil

Thanks Neil - I'll check to see which of these handbooks I have, or can access, as well as the 1959 Publication. Trevor

 

[Bonnex]

The attached table will, I hope, be of interest. I am sorry that it is a rather difficult 'read'.