ID Question on 25mm round

[ajf.350d]

Just got these two 25mm rounds.
Obviously one of them is one of the saboted type rounds, but not sure what the other is?
Seems to be an unusual shape. The base unscrews as whislst it is crimped in you can unscrew the projectile from it.
The case also seems to have 'shoulders' added to the neck area.

Andrew

 

[Chris 42 RQ]

I think you may well have a 25mm Oerlikon or perhaps Bushmaster round !
The projectile looks like it is an AP with the soft streamlined nose cap missing (presumably never put on during manufacture), if it has an alloy base plug (LH threaded) then it could be an APSE Armour Piercing Special Effect, simply an AP projo with a nasty red phosphorus filling which ingnites by means of heat and impact on contact with a hard enough target.
The blue APDS type projo may well be missing its streamlined nose cap too !
My money is on it being of Oerlikon origen as they used to make a 30 mm version many moons ago.
What is the headstamp of the cases please?
Nice rounds by the way !

 

[ajf.350d]

Thank you. I did wonder if it was missing a covering. The sabot round has lost its cap too at some point.
Picked them up of SA. The saboted round has no headstamps at all but there is a faint 'inert' stamp on the side.
The image below shows the stamps on the other one. I am terrible with threads but you turn counter clockwise to unscrew and it definitely looks like aluminium or similar.
Why the shoulders on the neck? Are they just for reinforcing or something for the handling mechanism?

 

[Chris 42 RQ]

Hi afj.350d in reply to your questions;-
The case is definately an Oerlikon.
But I am a little unsure what you mean about "the shoulders on the neck" so I will try to cover all angles here-
The ring you can see on your Oerlikon fired case about three fifths of the way down from the top of the neck is an indent groove for the "link" to locate in to maintain the round in the correct position within the belt of simliar rounds, on firing this flattens out and almost dissapears due to the pressures involved.
The uppermost indents (around the neck at regular intervals) are for crimping in the projectile to make it watertight and secure.
The small raised sections from the top of the case going down the shoulder of the case are in effect an imprint taken from the inside of the chamber as the weapons chamber is "fluted" so that the case can be easily extracted, on firing the case expands to fit the chamber and because the steel case cannot deform to an exact fit it reduces the area of contact allowing easy extraction.
Hope that helps ?
Almost forgot-your case headstamp reads=Oe - Oerlikon 69 - date of manufacture 1969 23 is Lot number or Batch number. and the small "psw" is the steel case manufacturers monica !

 

[ajf.350d]

Sorry, confused you using the term 'shoulder' I have taken another photo and circled the part I mean. It looks like an additional bit added on is the best way of describing it. In other words if you took a 'slice' at that point it would not be circular is in most other shells I have seen.
The fluting I assume you mean are the vertical dark 'stripes'?

 

[Chris 42 RQ]

Hi ajf.350d yes sorry I now know what you mean-this again is a section of chamber that is machined away to aid the loading of a full length round, at some point it was found that with rapid loading it could happen that a fuze got damaged due to the side of the fuze striking the chamber during the loading cycle.
The anmswer to that problem was to make a small cutout in the chamber which would allow plenty of clearance between the fuze and the side of the chamber-you will find that these expansion marks are on a lot of fired Oerlikon rounds in 25 mm, 30 mm and 35 mm calibres.
Hope that explains the "bulge" you find on your case.

 

[ajf.350d]

Many thanks for the information here. Now you say it, obvious it is a 'bulge' I couldn't think of the right word at the time.
It is quite amazing to think that they have been created through the firing process, but then again having just obtained a 155mm round and nearly knackered my back lifting it, it does show the forces required to fire these things!

Andrew