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German 20x108cm

O

orcutteod

Well-Known Member
Enclosed are pictures of an German WWII 20x108cm shell. This varriation I must confess I'm not that familiar with any more info is most appreciated.
 

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It is not German. It is a British 20mm Oerlikon made at Royal Ordnance Factory Steeton in 1943. As it was loaded with nitrocellulose powder the "Z" was added to the "Oe".

All British Oerlikon rounds had the "universal" headstamp of "OeZ" and do not show load details.

Regards
TonyE
 
....although load details can be found on the side of the case,just above the extraction groove in the same manner as on 20x110 Hispano,on later British 20x110 Oerlikons.....also the fired example shown does not have the same shoulder and neck profile as an unfired example due to the Oerlikon gun starting to extract the case before completion of the firing process therefore 'blowing' the neck and shoulder out,which may explain the 108mm case measurement

Cheers
Tony
 
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Is that actually so, Tony? Surely the Oerlikon is an advanced primer ignition system and fires the round BEFORE it is fully chambered thus expanding the shoulder. It then stops the breech block on its forward travel amd starts the recoil and recycle process.

Regards
TonyE
 
Isn't that just another way of saying 'starting to extract the case before completion of the firing process'? process defined as " a series of actions or steps taken in order to achieve a particular end"....also as you say 'BEFORE it is fully chambered',are you saying it does fully chamber?...if this is the case then surely the rather hot brass case would take on the form of the chamber and be extracted/ejected without a 'blown out' shoulder and neck?

Regards
Tony
 
smle2009 said:
Isn't that just another way of saying 'starting to extract the case before completion of the firing process'? process defined as " a series of actions or steps taken in order to achieve a particular end"....also as you say 'BEFORE it is fully chambered',are you saying it does fully chamber?...if this is the case then surely the rather hot brass case would take on the form of the chamber and be extracted/ejected without a 'blown out' shoulder and neck?

Regards
Tony
Click to expand...

We are digressing from the thread here, but no, I don't think it is the same thing. The Oerlikon fires whilst the round is on its way forward and takes the form of the chamber at that point. By the time the breech block has reversed direction to recoil the pressure has already dropped.

We are probably arguing about angels on the head of a pin anyway as we both know what we mean!

Cheers
TonyE
 
Good piece on Oerlikon & API by Tony Williams ............http://www.quarry.nildram.co.uk/apib.html For correctness, I think Tony E you are right, as the round is fired while still travelling forward and by the time the extraction process is taking place the firing process is actually complete - i.e. it doesn't extract before the firing process completes. Not that this matters, but I just wanted to get my own head round it, hence working it through by writing it down! I guess its good to get it right though as its the basis of how the Oerlikon functions and all that!
 
I wasn't arguing boss,I was asking questions,you know more about these things than I ever will!.....mind you I have never seen angels on a pin head but I did see an elf on a toadstall once! :tinysmile_shy_t:
Mark I didn't say it extracted before the firing process completes,that would be a rather stupid thing to happen,I said it started to extract and even after reading Tony Williams piece it seems to amount to the same thing to me?

One point of interest I have come across concerning the original thread....I had a 'grub around' in my 'odds and sods' box and pulled out fired Oerlikon cases,three of them were ST manufactured and all had the identical base distortion as the one in the first post yet RG,RH and R.C.C did not....so could this base distortion be unique to ST?

Cheers
Tony
 
smle2009 said:
I wasn't arguing boss,I was asking questions,you know more about these things than I ever will!.....mind you I have never seen angels on a pin head but I did see an elf on a toadstall once! :tinysmile_shy_t:
Mark I didn't say it extracted before the firing process completes,that would be a rather stupid thing to happen,I said it started to extract and even after reading Tony Williams piece it seems to amount to the same thing to me?

One point of interest I have come across concerning the original thread....I had a 'grub around' in my 'odds and sods' box and pulled out fired Oerlikon cases,three of them were ST manufactured and all had the identical base distortion as the one in the first post yet RG,RH and R.C.C did not....so could this base distortion be unique to ST?

Cheers
Tony
Click to expand...

Mmmm? Were you eating the toadstools at the time?

Perhaps I should not have said arguing, more of a gentlemanly discussion!

Cheers
tonyE
 
smle2009 said:
....although load details can be found on the side of the case,just above the extraction groove in the same manner as on 20x110 Hispano,on later British 20x110 Oerlikons.....also the fired example shown does not have the same shoulder and neck profile as an unfired example due to the Oerlikon gun starting to extract the case before completion of the firing process therefore 'blowing' the neck and shoulder out,which may explain the 108mm case measurement

Cheers
Tony
Click to expand...

Your explanation helps explain the confusion I had trying to ID this shell.
 
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