RAF 20mm Hispano and 40mm Vickers 'S' help

[Brennan]

Hello folks, great forum and contributers you have here. Spent quite a long time just reading all the threads from way back.

Anyway, I'm working on a project that deals with RAF ammunition, and I was wondering if anyone could help me with a few aspects of the types mentioned in the title.

20mm Hispano:
tracer mk.I
- does anyone have the composition/filling of this round?
- any data out there with regards to its penetration?

cartridge case
- does anyone have a cutaway image or diagram?

40mm Vickers 'S':
armour-piercing and high-explosive
Well I'm really in trouble with this one, I can't find any information or sectioned images on these rounds. I have data and and an image on the AP Mk.VI, and that's it.

Specifically I'm looking for the marque of AP and HE rounds that were the most common/used. I have a feeling the AP Mk.VI is a later round.

Thanks for any help.

 

[TonyE]

Drawings

I am afraid I cannot help you on the penetration of the Hispano tracer. I have checked both the British and American ammunition manuals and no figures are given. It will be the same as the ball, so if you can find a figure for that it will help.

Attached is a drawing of the Hispano tracer, dated 1940. I have plenty of other drawings but most are too big to post. I will PM you with my e-mail address.

As for the 40mm Class S, you need Tony Williams. 40mm is outside my collecting and data range unfortunately.

Regards
TonyE

 

[Brennan]

That image is perfect thank you. A couple of follow up questions, though:

10 grams of 'inert material'; was there a standard substance used?
5.2 grams of 'w.composition'; any indications as to what this was made of?
Do the manuals give any data with regards to how long or far the tracer burns?

Thanks again.

 

[SG500]

S gun article

Hi, Tony Williams web site has a good article on the S gun and its ammunition. I'm sure he'll log on later and give more detail.
The link is as follows.
Dave.

http://www.quarry.nildram.co.uk/sgun.htm

 

[Falcon]

10 grams of 'inert material'; was there a standard substance used?

Thanks again.

It says at the top that it is a mixture of 70% Clay and 30% Graphite, in case you didn't see that.

Tony, were the projectile bodies for tracer and TP the same?

 

[Tony Williams]

That article of mine referenced above includes just about all I know about S Gun ammunition. The Mk I and heavier Mk VI seem to have been the service AP types (they fired HE as well, of course). I have no idea what happened to the Mks II-V.

I think that the Mk VI was identical in external shape to the MK I but had a smaller (or no) internal cavity, but I couldn't quote a source for that and I have no sectioned drawings of the AP rounds.

 

[StielGr]

40mm Vickers 'S':
armour-piercing and high-explosive
Well I'm really in trouble with this one, I can't find any information or sectioned images on these rounds. I have data and and an image on the AP Mk.VI, and that's it.

Specifically I'm looking for the marque of AP and HE rounds that were the most common/used. I have a feeling the AP Mk.VI is a later round.

Thanks for any help.

There are some other links mention in this previous thread:
http://www.bocn.co.uk/vbforum/vickers-class-s-t21868.html

And this particular link has some numbers mentioned:
http://www.wwiiequipment.com/vickerss.aspx

Can you post your data and image on your AP Mk. VI please?
It would be much appreciated.

PC

 

[SG500]

Some photos of a couple of S gun rounds plus the headstamp (note the AP on the stencling).

Stamping on the projectiles is as follows:

40 M/M A.P. SHOT
H.LTD
374
5'42
AV159.8
AM

Plus crows foot etc.

Dave.

 

[StielGr]

Dave
As far as I know from the limited information available the S gun case was identical to the common Naval 2pdr No. 1 but did have a distinctive headstamp.
The S gun headstamp was marked "2 PR/40 S No.1"
This case is extremely rare.

Thank you for the picture of the rounds...very nice.
Would it be possible to see the base of the projectiles for the tracer cavity?

Regards
PC

 

[SG500]

Hi PC the cases aren't all marked 2 PR/40 S No.1. I've come across about 7 S gun rounds over the years and none have this marking on them so either someone many years ago got a job lot of projectiles and crimped them into cases that didn't have that stamping on them or they used some that weren't stamped as such - I have seen a photo of one with the stampings you mention though.
The 2 rounds I have came from completely different sources but are both very similar - they're the heavier ap versions (Mk IV) with the smaller cavity.
I can't take a photo of the bases of the projectiles however can confirm that neither have a tracer cavity. The S gun projectiles are partly hollow but the cavity is not filled with HE as with German rounds but closed with a base plate. This has 2 small holes (that don't go all the way through the plate) in it on opposite sides of the plate and these can be seen through the primer hole in the case.
Hope this helps.
Dave.

 

[SG500]

Done it!!

I thought I'd try anyway and if any of you haven't tried taking a photo of the base projectile through a primer hole, well you have to stand on your head to do it!!

Ignore the bright ring in the photo, that's the light from the torch, the bit in the middle is base of the projectile and the small holes can clearly be seen.

Dave.

 

[Tony Williams]

There was a problem with some of the 40x158R naval cases when used in the S Gun: IIRC their brass was too soft, leading to extraction problems. These came from one maker, so they had to acquire S Gun cases from another. I forget the exact details but I can do some digging if anyone's interested.

 

[SG500]

Hi Tony, I'm interested, would you do some digging please.
Thanks.
Dave.

 

[Tony Williams]

I found the reference, in Wallace's Guns of the Royal Air Force. This states that 40x158R cases were made by Kynoch and Vickers, with Kynoch making most of them. The problem with soft brass applied to the Kynoch cases; extraction could be so difficult that the rim was torn off by the extractor. Apparently it wasn't possible to specify that only Vickers cases should be used, so it was agreed that the usual British ban on the use of oiled cases would be lifted for the S Gun (as it was for the 20mm Oerlikon), and the ammo was duly oiled.

 

[Tony Williams]

Incidentally, according to Wallace the RAF also had a problem with 20mm Hispano cases, which the French (and the Americans) oiled, since the gun was a delayed blowback without positive case extraction. The MoD refused to accept oiled ammo, so the cases were modified in some unspecified way. It is generally felt that what they probably did was to coat the cases in hard wax, but I don't know if any evidence for that has been found.

 

[StielGr]

The 2 rounds I have came from completely different sources but are both very similar - they're the heavier ap versions (Mk IV) with the smaller cavity.
I can't take a photo of the bases of the projectiles however can confirm that neither have a tracer cavity. The S gun projectiles are partly hollow but the cavity is not filled with HE as with German rounds but closed with a base plate. This has 2 small holes (that don't go all the way through the plate) in it on opposite sides of the plate and these can be seen through the primer hole in the case.
Hope this helps.
Dave.

Hi Dave
You did a good job of standing on your head.....:tinysmile_shy_t:.....what I mean is well done on the picture as it shows the base in nice detail.

Maybe Tony can answer this question but due to the lack of sectioned diagrams I had always assumed that only the lighter AP Mk 1 had the base cavity sealed with a base plate.
There is reference to the 3lb Mk VI with and without tracer. The Mk VI with tracer being more common.

My problem is I am still not sure if my projectile is for the S gun. Although is does have the right weight.

PC

 

[Tony Williams]

The projectile shown in your picture has the right shape for an S Gun also. The early naval rounds had some pointed steel SAP with base fuzes but the shape was different: as you can see in the pic below:

 

[SG500]

I can't remember where I got these pictures from so apologies if I've stepped on anyones feet - they give an idea of what the S gun AP projectile looks like.
Dave.

 

[2pounder]

40mm Vickers S gun and Rolls Royce BH gun AP

sectioned view taken from Provisional Ammunition Memorandum hope it helps, the above documents have loads of important info in but am not sure which library they are held in, I was fortuneate to be given part of one, so well worth researching if thats your thing. At the risk of telling old hands what they know but it might help beginners: beware a mkV round wont nescessarily have a mkV shell so check if data refers to round mark of shell mark
AP -MK. I,I*,II,II*,V and VT (40mm SBH gun QF ammunition),
mkI with 2lb 7oz shot.
mkI* similar but with modified shot.
mkII similar to mkIround but with temperate propelling charge.
mkII* similar to mkII round but with modified shot.
mkV with 3lb shot and world wide propellant.
mkVT similar to mkV but fitted with tracer.
mkI* and II* have no base plug so are lighter by 2oz.

cases are common to all mks and use no.27 primer.
MkV shot are solid and have a tracer cavity in the base, mkVT have the tracer cavity filled.

There are also HE and practice rounds of various marks.

 

[StielGr]

Thank you Dave & Tony. I have a similar picture stored in my archive but that is the only section diagram I have ever seen

MkV shot are solid and have a tracer cavity in the base, mkVT have the tracer cavity filled.

Thanks 2pounder
Would I be correct to assume that the projectile I have is a Mk V?

PC