Questions about British large-calibre cartridge case relationships

[Tony Williams]

I am looking for some help from the experts on 3+ inch British cartridge cases, especially of the WW2 era; I'm interested in pinning down their dimensions and any relationships which may have existed between them (as indicated by the rim diameters). I am outside my comfort zone here because I don't generally collect such large ammo.

For instance, I didn't realise until recently that the WW1 18pr field gun used almost exactly the same case as the succeeding WW2 25pr, only necked out a bit (84 x 295R, vs 88 x 292R, both with rim diameters of 103-105mm).

I have also discovered that the 17pr case (76.2 x 583R) may have been based on the 3.7" Mks 1-3 AA gun (94 x 675R), since both have 135mm rims.

A couple of myths around relationships have sprung up. For instance, that the experimental 32pr (94mm) AFV/AT gun used the same ammo as the 3.7" Mks 1-3 AA, whereas it used a longer (909mm) straight case with a smaller rim (anyone know the diameter?). Another myth is that the big 3.7" Mk 6 AA gun, based on the 4.5" AA, used a necked-down 4.5" case, but in fact the rim diameter of the 4.5" (114 x 640-700R) is 167mm while the 3.7" Mk 6 (94 x 587R) is 150mm. Interestingly, the WW2 4" L/45 naval gun case (102 x 730R) also has a 150mm rim, so perhaps the 3.7" Mk 6 was based on that?

I note that the standard RN 4.7" L/45 destroyer gun of WW2 used a 120 x 775R case with a 154mm rim. However, I don't have any dimensions for the 4.7" L/50 case (QF Mk XI) used only in a few L and M class destroyers. Can anyone help?

Also, does anyone have the case dimensions for the 5.25" naval gun?

Thanks in advance!

 

[kahu1]

Case dimension of 5.25" ,133 x 778R ,rim dia.185mm.
Regarding the 25pr,I heard a story of some British EOD working in Venezuela in 1980s or 90s, got quite excited to see the Venezuelan Army 88mm guns,thinking they were German Flak 88s. A bit dissapointed to find they were only 25pr's in metric!.

cheers
Bob

 

[charley777]

Hello Tony...actually the 18Pr and 25Pr cases are different. Put them side by side and one will notice that the 25Pr is not only larger in rim size but also the case above the rim is a couple of mm larger. So the 25Pr would not chamber in an 18Pr breech, whereas there would be quite a mess if one fired an 18Pr in a 25Pr breech.
Here is my 4.7inch (120mm) list...sorry, havn't had time to extract the UK cases....
OK, technical problem, can't attach Excel sheet (my ignorance, no doubt).
Will email it to you

 

[Tony Williams]

Thanks Charley, your list is very interesting.

The case for the 4.7" L45 Mk IX and XII guns is 775mm long with a 154mm rim (our sources agree on that). You list the L50 Mk XI case as being 716mm long (rim diameter not known). As Conway states that the Mk XI chamber volume was slightly larger (6.7%) than the Mk IV and XII, this implies that it must have been significantly fatter, with a wider rim. Must keep looking....

 

[charley777]

Tony.
Having reread your original thread post, i see that you want more info on UK naval cases over 3inch.
When i get time i'll compile a list of all those i have info on and send it on to you. There are quite a few...

 

[2pounder]

Tony,
the later (by 1949) 5.25in LS was the same case but had a different closure method to the three tags on the earlier naval. Not sure if the LS was introduced at the same time and used the same rounds nor if the 1949 naval had the adaptor and screw in plug system ofthe LS. If you want photos of the 1949 I've got one and think its been posted a while ago.

 

[Tony Williams]

Yes please, that would be interesting to see.

 

[2pounder]

couple of photos of my 5.25in case dated 1949. showing the closure method.