40x158R (Edit: 2 pr No.1.....{British?} naval AA “Pom Pom”)

Shell case with screw in primer…no headstamp.

Looking at previous Forum topics, it would appear to be a Vickers-Armstrong (2 Pdr).

Dimensions in mm

Case length: 158
Rim: 47.96
Neck: 40.50
Head: 43.87

Would be grateful for any additional ID, or background information.


Yes, it’s a 2 pr No.1 case for the British naval AA “Pom Pom”. First used in WW1, extensively used in WW2. I am not an expert on headstamps but the lack of a headstamp indicates that this was not made for British use. There were various other users of the 2 pr including the Japanese Navy, which bought it in some numbers in the interwar period, before replacing it with the 25 mm Hotchkiss.

Hi Tony,
Many thanks…and much appreciated.