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.303 inch ZPT ammunition

TonyE

TonyE

HONOURED MEMBER RIP
On 5th August 1918 Major E.Cadbury (pilot) and Captain R.Leckie (observer) attacked and destroyed Zeppelin L70 off the coast of Yarmouth. It was a particularly significant victory as Fregattenkapitan Strasser, the Leader of German Naval Airships was on board and was killed.

In his post combat report (now in the IWM archives) Cadbury states "....My observer trained his gun on the bow of the airship and the fire was seen to concentrate on a spot under the Zeppelin about 3/4 way aft. The Z.P.T. was seen to blow a great hole in the fabric and a fire started which quickly ran along the entire length of the airship."

In the official history of the Air War (Vol. 5, p.132) Jones quotes this report and adds a footnote "Z.P.T. refers to the Pomeroy tracer bullet in use at this time, known as the P.S.A. Mark II"

Apart from the fact that the Pomeroy was not a tracer, has anyone ever seen any other reference to the term "Z.P.T." for the P.S.A. Mark II?

I cannot think of any reasonable explanation for "ZPT" although the "Z" may refer to nitrocellulose propellant and "P" for Pomeroy.

Thanks,
TonyE
 
Tony,

Might the Z simply be for Zeppelin? I only have an incomplete index of Ordnance Committee minutes, but OC minute 7553 is 'Incendiary Projectiles, Zeppelins. Shells for use against Zeppelins to be distinguished by the letters "A.Z." '




Tom.
 
Tony - the only trouble is that the Pomeroy was not a tracer. it did not leave a trail of any kind, either smoke or flame.

Snufkin - I will look up that OB Proc. but I suspect it applies to A.A. ammunition rather than small arms ammo. The approval document for the PSA Mark II states it is "VII A.A." with no mention of Zepellin in the nomenclature. Thanks for the suggestins anyway.

Unless I can find any further evidence it will have to be just another little mystery in my thesis!

Regards
TonyE
 
was just a guess boss and Jones footnote did refer to it as "Z.P.T. refers to the Pomeroy tracer bullet in use at this time,known as the P.S.A. Mark II?".....although not a tracer could it have been wrongly termed as such at the time?


Cheers
Tony
 
The incendiary and anti-balloon bullets seem to have three letter codes. Using the contemporary July 1917 Threlfall bullet as a possible guide the first version was known as the RTS, with an incendiary composition. An experimental version with HE filling was designated RTT, although it was too late to see use in WWI. Therefore might the final letter be a code for the filling, S for incendiary and T for high explosive? In which case the T in ZPT would be appropriate.

It appears that one of the three letters might be for the name of the designer or company making the round... TonyE - is this the case? So first letter S in SPG and SPK for Sparklet, B in BIK for Brock? Then a shift to the second letter at some point so the T in RTS and RTT for Threlfall. The corollary being that the P in ZPT is Pomeroy?




Tom.
 
RTS is for "Richard Threlfall & Son" whilst RTT is for "Richard Threlfall & Todhunter (Col. Todhunter of the Design Department at Woolwich).

I believe the way the codes worked was for the first letter of the designer was used (e.g. VIIB for Buckingham) then if that was already allocated the last letter was used (hence VIIK for Brock). If that was already used then the second letter applied so that with both "B" and "K" allocated, "L" was used for blank when new codes were allocated in 1926.

That system neatly explains every code except "Q" which was allocated for proof in 1926. However since P, F, R and O were already in use then "Q" was the next letter after "P".

The letter allocated to Pomeroy was "Y", being the last letter of his name because "P" had already been allocated for an earlier "Penetrating" armour piercing round. I have design drawings showing the Pomeroy as the Mark VIIY.

I am still not sure of any logical explanation for "ZPT".

Regards
TonyE
 
Tony,

Thank you very much for the explanation. All I can say is good luck with your quest.

What is the full deciphering of the Brock round BIK and the Pomeroy PSA? I'm losing track of the logic.



Tom.
 
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I believe the nomenclature "BIK" translates as "Brock Incendiary K" although I have no proof of this. Even the Woolwich record of the approval in the files only shows "VII BIK" with no further explanation.

"PSA" stands for "Pomeroy Special Ammunition", something dreamed up by Pomeroy himself.

It has taken me years looking at the files to hopefully gain some understanding of the way the nomenclature was allocated. AFAIK, I am the first person to have (hopefully) cracked the code of the letters allocated to the various natures of special ammunition.

Although the drawings exist (and I have copies) there are no known rounds headstamped either "VIIK" for Brock or "VIIY" for Pomeroy. All the Brocks known have ball headstamps (often E 16 VII) and PSA Mark I are usually also ball with the same headstamp whilst PSA Mark II are headstamped "VIIAA". The latter is probably for "Anti-Airship" rather than Anti-Aircraft as Pomeroys were supposedly only to be used against Zepellins by Home Defence squadrons.

Regards
TonyE
 
Thanks again Tony.

Turning to the Sparklet rounds SPK and SPG, is it the case that the S is indeed for Sparklet? But the K, that is surely not Brock? Considering the example of the BIK round...

Are "Richard Threlfall & Son" for RTS and "Richard Threlfall & Todhunter" for RTT confirmed in the documentary record? They seem to be completely at odds with the other three letter codes, although all seem to have a degree of randomness.





Tom.
 
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