12 pdr 12 cwt 25 oz torpedo impulse case

[Dronic69]

Good Morning All,


I'm looking for any information regarding the re-purpose use of a naval 12 pdr 12 CWT case for adoption to a torpedo impulse case - diagrams, descriptions pics?

There has been past threads on this topic in general:
http://www.bocn.co.uk/vbforum/threads/92594-Cut-down-3-pounder-Case?highlight=impulse+torpedo

http://www.bocn.co.uk/vbforum/threads/82296-impulse-torpedo-cartridges?highlight=impulse+torpedo


However there is an interesting note in the following thread:
http://www.bocn.co.uk/vbforum/threads/3889-Cartridges-Impulse-Torpedo-c-1915


In regards to a special charge for the HMS Swiftsure & Triump which states that the impulse case was "similar" to the QF 12 pdr 12 cwt case, which was used with the 18" submerged tubes.

Any info would be greatly appreciated.

Thanks
Cheers
Drew

 

[Dronic69]

No comments or thoughts?

I noticed that Spotter 's reference only goes up to 10 oz (~1915). I'm particularly interested in the interwar to WW2 period i.e. larger fills - around the 25 oz sizes which would deem the re-purpose of larger calibre cases.

Thanks
Cheers
Drew

 

[Dronic69]

The reason for this thread is due to a recent find (yeah I know I'm suppose to be collecting only fuzes now!!!)

This is a very interesting case: (apart from the fact that I have never seen one before)

1) Original Markings: 12 pdr 12 CWT Mk 1 N 1917 CF R^L
2) Later conversion to torpedo impulse case: 25 oz (initially 30 0z?) 1928 (well I assuming at this stage)

Certainly has the typical re-purpose to a torpedo impulse case characteristics:

> Officially Shortened (visible signs of lathe turned on the inside of the top / internal colour differences)
> Based stamp with a "oz" weight (i.e. 25 oz)
> Long internal primer - top is 1cm below case mouth (fits in with first point above)
> Case mouth "scallop" notches - hum, is this normal as most were smaller twin notch pairs?
> Inter-war period experimental case? (30 oz stamp striked out and replace with 25 oz)

Any information /thoughts would be great - not sure why the base was lead sealed - perhaps further "re-purpose" as a vase???

Thanks
Cheers
Drew

 

[ammofo]

Hi Drew, with regards to the other source stopping at 10oz, I have an 1899 dated repurposed 3lbr marked up at 12oz which I uploaded on an ID forum in the past. Perhaps this won't bring you much extra info, but it's worth a mention. As for the lead solder on the bottom, I've seen that many a time on 'trench art' French 75mms and you're spot on with the vase theory !! Sorry I can't be of more help...

 

[ammofo]

...perhaps only to add that mine also has internal evidence of lathing and a very slightly inwardly curling lip at the mouth.

 

[Dronic69]

Hi Drew, with regards to the other source stopping at 10oz, I have an 1899 dated repurposed 3lbr marked up at 12oz which I uploaded on an ID forum in the past. Perhaps this won't bring you much extra info, but it's worth a mention. As for the lead solder on the bottom, I've seen that many a time on 'trench art' French 75mms and you're spot on with the vase theory !! Sorry I can't be of more help...

Hi Ammofo,

Firstly thank you for sharing your thoughts!

Yes I have seen others ~1900 cases marked at 12 oz - which is interesting as to why there is no mentioned in the 1915 publication (surely there must be a later date publication?) - does your example have an accompanying date stamped when the conversion was done?

The slight inward curving at the top is normal and typically done during the conversion during this period.

The unsolved question is whether this method was changed in the late 1920? (1928) ie no inward curving and single larger scallop notch instead of a double one.
From memory I thought double notches were still done during WW2 with no inward curving?
If so then this aligns with my trench art vase theory as there is certainly no other apparent visible modifications..........I'm just going to have to de-commission it from vase status and remove the lead :tinysmile_twink_t2:

On the other hand, the notches were purposely done this way (i.e. experimental/crossed out 30 oz stamp?) and it is an intact perfect example.

Either-way it is in near perfect condition and IMHO may be rarer than rocking horse poo???

Thanks

Cheers
Drew

 

[ron3350]

Not 12Pr but I have some 3Pr Impulse cases with extended primers and 3 sets of mouth cut-outs. Stamped Mk1V and MkV 17oz.
The difference seems to be the primer adaptor. Both have 40 holes in the primer magazine. ie 8 rows of 5 holes.
Case length is 265mm.

The case EOC 6/01 has 2 mouth slits for some reason. It is 247mm case length. It has a short primer. Blank or trench art? Ron.

 

[Dronic69]

Hi Ron,

Thanks for posting - very nice mid -1920s examples & very interesting deed for comparison!!!

A couple of observations:
> Seems at least mid to late 1920s, the case mouths are straight edges - not slightly curled over as per the earlier ~1900 examples that have been posted on the forum.
> The number of primer flash holes & hole sizes have varied from approx. 18 to later period of 40
> The number of primer flash holes may depend on the size of the case calibre size - i.e. 3 pdr /6 pdr /12 pdr - for example my 12 pdr has just 4 x 5mm holes situated at the top of the primer (see pic)
> It seems that all related torpedo impulse cases are marked with the charge in "oz" - was this solely used only on impulse cases? (although I do recall seeing post-war (1950/1960s) cases with stenciled on the case side with charges in oz) Or was this adapted for blanks /signal purposes as well? I ask as I have not seen any blank /signal purpose cases marked in "oz" (but then I do lead a shelter life). Further, if blanks etc were marked with the charge weight, would the final differential between a blank etc and an impulse case be the extended length of the primer? All thoughts welcome.


Finally i decided to explore and remove the lead from the bottom of the case - found the original primer /socket under a heap of lead - my vase theory may have been correct as there was also a wood dowel stuff inside to reduce the filling (actually was quite a shit job as the case bottom wasn't even level with the lead filling!)

So apart from what I'm assuming were the original reloads when it was a 12pdr 12 cwt (C.F *), it seems that it was re-purposed in 1927, filled with 30 oz, then modified again to 25oz (1928) [Note the 1927/28 date stamps]

Summarizing the case characteristics"

1) Used with difference charge loads;
2) Deviation from the normal mouth cut-outs (scallop)
3) Larger but fewer primer holes.

Was this an experimental /test torpedo impulse test case? (is it a torpedo impulse case?)

Ho hum, more questions....................

Finally any ideas on the red circle markings? Inspector stamps? I have seen the circled "JK" before somewhere - similarly for the small rowlock symbol crossed out. "GH"?

Thanks
Cheers
Drew

 

[Dronic69]

Just some further thoughts in general:

Any ideas on what was the largest amount of charge used, including use for say later WW2 A/S mortar etc? (I have only seen up to 25 oz?)

Prior to WW2, were only torpedo impulse cases stamped with the filled charge in oz? What about other re-purposed cases for blanks /signalling etc?

Were only the torpedo impulse cases had the extended almost case length internal primers?

I'm assuming that the stamping /marking of impulse purpose cases changed during the WW2 /post war period as the attached Mk5 case has "IMPULSE" stamped on the base and the charge fill stenciled on the side - although it appears to have been "overhauled" in 1956?

All thoughts welcome.
Thanks
Cheers
Drew

BTW - Photos courtesy of the IAA site