20mm Shell Casing ID help

Hi everybody,

While out metal detecting on our private permission in Somerset (UK) we found five 20mm shell casings all dated the same 1943 and all with the same manufacturers stamp. Here’s the best one below. My question is does anyone have any idea, who made them and what fired them? I have heard everything from Spitfires, Hurricanes, B17’S, to Anti Air on the ground. A bit of basic reasearch hasn’t made things any clearer. Locally there was no AA stationed at the site they were found on, (Near Weston-Super-Mare UK) and the casings were all found in line over three fields, so obviously fired from an aircraft as it went over, but does anyone know what type of aircraft? The local WWII squadron was made up of Hurricanes, but i’m told the casings are American. If that’s the case, it would seem slightly out of place in rural UK circa 1943. (As a new user i can only post one image, so here’s the bottom of the casing. Overall each shell casing is 5 inches long.

This is a 20x110 HS case made in the US in 1943 (Symington Machine Corp, Rochester, New York).
5-inch would be 127mm.

As this caliber was standard on many figthers it could have been used by plenty of US or UK aircraft.

Thanks for the info EOD. As i know little to nothing about the subject, what does HS stand for? And would these have been standard rounds for British Hurricanes circa 1943?

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Alex, this “S.M.C.” was Stoner Manufacturing Co. of Aurora, Illinois.



Fede, thanks! I took it off the IAA hs database…

Scarabrae, 1943 or later could be entirely possible for this case including Hurricanes and many many others. Basicall all fighters armed with a 20mm back then.
The HS is the general gun / caliber designation and means “Hispano Suiza”.

Great info, thank you both very much. I assume these would have been made in the US and exported to the U.K due to our lack of resources at the time.

I do not know how much of this particular caliber was delivered to the UK during war.
Keep in mind that there were also plenty of US planes flying around!

I have done a little more digging, and by using this history of crashed German aircraft in, near and around Bristol/Somerset throughout the war. (there is very little chance of it being a US aircraft in 43.) I’m going to pin it on a De Havilland Mosquito. There were Hurricanes of 10 group in the area, but none saw any notable local action in 43, or so i gather. Instead jump to 44 and you have Mossies shooting up everything in sight. Really who or what fired them, must remain a mystery. Thanks for all your help folks. Here’s the list below, it’s very interesting.


U.S. fighters in the European/Mediterranean theater were overwhelmingly armed with Browning .50 cal MGs. A significant exception is the P-38, of which some were armed in part with a 20 m/m Hispano. The P-39 carried the Hispano in some subtypes, but was a relatively brief player in the Mediterranean theater. Jack