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Historical loadout for RAF Guns


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From this source: 

 

Guns of the Royal Air Force 1939-1945.: Amazon.co.uk: Wallace, G.F.: 9780718303624: Books

 

for the 20mm Hispano :

 

  Quote

For the latter half of the war the standard ammunition for fixed gun fighters was a 50-50 mixture of HE/I and SAP/I.

 

Where the HE/I was designed thus:

  Quote

During experiments to develop an incendiary [20mm] shell the effect of adding an  incendiary pellet to the HE shell was tried. It's performance against petrol tanks was impressive; it was far more effective than either the [plain] HE shell or the plain incendiary.

 

In 1940 the De Wilde type of incendiary composition was used and a High Explosive-Incendiary shell containing equal amounts of HE and Incendiary composition was approved..... it completely replaced the HE shall and remained in use until the end of the war.

 

The original [Hispano design] percussion nose fuze fitted to the 20mm shell was expensive, difficult to make and had a centrifugal safety device. One of its main troubles was that it was so sensitive that the shell would explode on the surface of an aeroplane, doing only superficial damage. It would be far more effective if it penetrated into the aircraft structure before exploding... [because of this the British] developed the the striker-less fuze which was known as 'Fuze Percussion D.A. No. 253 Mark I'. It was fitted... on all the HE/I. Besides being cheaper and easier to make... it gave sufficient delay in operation to allow the shell to penetrate some distance into the aeroplane structure before exploding.

 

 

Where the SAP/I (Semi-Armour Piercing/Incendiary) was designed thus:

  Quote

By the end of 1940 the Germans were armouring their aircraft; in particular they were providing armour protection for for their self sealing fuel tanks. The Ball ammunition then in use would penetrate the armour without difficulty, but had little incendiary effect. The HE shell had good incendiary effect but detonated on the surface of the armour without penetrating to the petrol tank.

 

 In October [1940] the War office Design Department was asked to design a shell which would penetrate armour and also have some incendiary effect. During 1941 as a result of trials they evolved a shell which consisted of the standard HE shell body filled with Incendiary composition and having an Armour-Piercing tip in place of the fuse. Trials against 18mmm armour plate showed that the AP tip passed through the plate followed by the incendiary composition in flame whilst the shell body broke up on the plate. The penetration was better than the existing Ball ammunition, but not as good as a properly designed Armour-Piercing shell would be. It was however adequate for the conditions of the time as no armour over 12mm was being fitted by the Germans [to their aircraft].

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For historical accuracy please provide HEI and SAPI for RAF guns for the second half of WW2

 

From this source: 

 

Guns of the Royal Air Force 1939-1945.: Amazon.co.uk: Wallace, G.F.: 9780718303624: Books

 

for the 20mm Hispano :

 

  Quote
  Quote

For the latter half of the war the standard ammunition for fixed gun fighters was a 50-50 mixture of HE/I and SAP/I.

 

Where the HE/I was designed thus:

  Quote
  Quote

During experiments to develop an incendiary [20mm] shell the effect of adding an  incendiary pellet to the HE shell was tried. It's performance against petrol tanks was impressive; it was far more effective than either the [plain] HE shell or the plain incendiary.

 

In 1940 the De Wilde type of incendiary composition was used and a High Explosive-Incendiary shell containing equal amounts of HE and Incendiary composition was approved..... it completely replaced the HE shall and remained in use until the end of the war.

 

The original [Hispano design] percussion nose fuze fitted to the 20mm shell was expensive, difficult to make and had a centrifugal safety device. One of its main troubles was that it was so sensitive that the shell would explode on the surface of an aeroplane, doing only superficial damage. It would be far more effective if it penetrated into the aircraft structure before exploding... [because of this the British] developed the the striker-less fuze which was known as 'Fuze Percussion D.A. No. 253 Mark I'. It was fitted... on all the HE/I. Besides being cheaper and easier to make... it gave sufficient delay in operation to allow the shell to penetrate some distance into the aeroplane structure before exploding.

 

 

Where the SAP/I (Semi-Armour Piercing/Incendiary) was designed thus:

  Quote
  Quote

By the end of 1940 the Germans were armouring their aircraft; in particular they were providing armour protection for for their self sealing fuel tanks. The Ball ammunition then in use would penetrate the armour without difficulty, but had little incendiary effect. The HE shell had good incendiary effect but detonated on the surface of the armour without penetrating to the petrol tank.

 

 In October [1940] the War office Design Department was asked to design a shell which would penetrate armour and also have some incendiary effect. During 1941 as a result of trials they evolved a shell which consisted of the standard HE shell body filled with Incendiary composition and having an Armour-Piercing tip in place of the fuse. Trials against 18mmm armour plate showed that the AP tip passed through the plate followed by the incendiary composition in flame whilst the shell body broke up on the plate. The penetration was better than the existing Ball ammunition, but not as good as a properly designed Armour-Piercing shell would be. It was however adequate for the conditions of the time as no armour over 12mm was being fitted by the Germans [to their aircraft].

 

 

For example, this combat report from 7th March 1944 shows 150 rounds per cannon with 76 rounds S.A.P.I. and 74 rounds H.E.I. per gun for the Spitfire XIV.  This armament information is near the bottom of the report just above the signatures.

 

http://www.wwiiaircraftperformance.org/610_Harding_7march44.pdf

 

Thank you for your consideration.

 

Happy landings,

 

Talisman

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On 4/16/2021 at 2:52 PM, ACG_Talisman said:

It would be far more effective if it penetrated into the aircraft structure before exploding... [because of this the British] developed the the striker-less fuze which was known as 'Fuze Percussion D.A. No. 253 Mark I'. It was fitted... on all the HE/I. Besides being cheaper and easier to make... it gave sufficient delay in operation to allow the shell to penetrate some distance into the aeroplane structure before exploding.

 

Interesting read. Is there any source material how this delay was archived and how much delay there was? e.g. the germans used an additional delay charge for 20cm-75cm delay after impact.

The allied manuels for the PD 253 Mk 1-3 fuze give no hints on any additional delay. they describe the fuze as "instantanious action upon impact on ligh material surface".

Same for is succecssor the M75 Fuze and the M97 HE-I round intruduced in June ´44, which gained improved ballistics due to the M75 fuze being pointed and the M97 HE-I round beeing heavier (131g) while losing some of its HE-I filling (0.012lbs Tetryl and 0.005lbs Incendiary/5.44g Tetryl and 2,27g incendiary filling for the M97 HE-I vs 0.025lbs HE-I filling for the MK I HE-I with the PD 253 Mk 1-3 fuze). The heavier bullet with the pointed fuze where introduced to have the same improved ballistics for all 20mm rounds in use, the M97 HE-I, the M96 Incendiarcy and the M75 AP-T, all sharing the same ballistics over 1000yards, having the same weight and improved pointed fuze/ballistic cap.

While carrieng less filling, the heavier bullet also gave better frag damage vs unarmoured targets (air and ground allike) and anti personel.

 

Cheers

 

Edited by the_emperor
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Hopefully others may chime in with more information and knowledge, as I am not so knowledgeable on the subject and just thought I would pass on information I happened to come across.

 

Happy landings,

 

Talisman

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Here is everthing I could compile from an old hard drive for the allied 20mm aircraft cannon (Hispano V).

M 75 AP-T

M 97 HE-I with the new pointed fuze

M 96 Incendiary

intruduced in June ´44

Cheers

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in a research paper from 1977 for the M505 fuze (a successor to the M75 fuze, also desrcibed as "superquick") I found some data on delay/penetration.

The "moddified fuze" is  the testsubject for more delay since the normal fuze was deemed insufficient.

image.png.ac0ecc87fc003ed9f7cae1ccaacb2811.png

Edited by the_emperor
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