20 x 110 Oerlikon query

[SG500]

This ones got me puzzled.
Its a 20mm Oerlikon round with a crimped in projectile and a struck primer.
The problem with it is that it appears to have been made from a fired round (this type of case typically blow out towards the top) but the crimping looks like its been done in the factory, certainly not by your average person in their shed:tinysmile_hmm_t2:
Has anyone any ideas about it?
Dave.

 

[Chris 42 RQ]

Oerlikon/Hispano

I think what you have there Dave is a normal 20 mm Oerlikon case fired in a Hispano chamber as you can see where the old neck line used to be.

I did once have a .50 Cal Browning round fired in a .55" Boys rifle which more or less swelled to fit the chamber very much as yours has done so.

As for the crimping I think it has been pulled which begs the question how can it retain the crimping marks having been fired ?
As with all these things-more questions than answers.

Interesting item and thanks for showing us.

 

[pzgr40]

Hi Chris , that's impossible. The rebated rim of the Oerlikon cannot be caught by the hook on the breachblock that pulls the shellcase out, as it is smaller than the Hispano's groove (in the base ) shellcase.
What we have here is -in my opinion - too much headspace, causing the shellcase to bulge out as the pressure is still in the barrel and the breech already moves backward. A lot of fired 20x110 RR shellcases look like that after being fired.
Regards, DJH

 

[Chris 42 RQ]

Pressure/Proof housing use?

Yes pzgr40 essentially I agree with you but my thoughts are that it has more than likely been fired from a barrel mounted in a pressure housing and you know that you can get away with an awful lot of "no no's" using such a mounting.
The .50cal in a boys barrel was using such a housing and had to be rod ejected which I recall being a sledge hammer job!

Do you not think the shoulder is a little too well formed for normal firing in the correct weapon!

Dave are there any signs at all of a small circular bulge (perhaps minute) in the case wall anywhere?
And what sort of AP projectile is that fitted into it as it is very short, could it be an APC without the cap ??????