enter image description hereBase of a shell casingBought this shell from an antique store. Would like to know the history behind it, as in what it was used for? (The casing is about 16 and 1/2 inches in length)

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    Purely as a matter of style, I'd suggest that since the base is marked "3 in" you could usefully give the length in inches. Commented Sep 23, 2023 at 7:30
  • Done, sorry, I automatically put it in cm. Wasn’t thinking. Thanks
    – Blake
    Commented Sep 24, 2023 at 13:06
  • bet you saw the "Cwt" and didn't really think what you were doing :-) Also note the "British Government broad arrow". Commented Sep 24, 2023 at 13:49

1 Answer 1


That appears to be a cartridge case for the QF 3-inch 20 cwt anti-aircraft gun. The "3in 20 cwt" marking on the base clearly indicates that.

That nomenclature means the gun fires 3-inch diameter projectiles, and the barrel and breech have a total weight of 20 hundredweight, or one long ton. That was a Royal Navy convention for gun designations, which I think originated in the nineteenth century and survived into the twentieth; larger guns were weighed in whole tons rather than hundredweight.

The gun was hastily introduced in 1914, when it was realised there were no suitable weapons for defence against German airships and bombers. It was designed and manufactured by Vickers. The design seems to have been based on the QF 12-pounder 18 cwt naval gun, with modifications to a War Office specification. It was used on ships and the Western Front, and stayed in use for second-line roles until 1947.

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    Ah! That’s awesome to know! Thanks, I appreciate it!
    – Blake
    Commented Sep 22, 2023 at 19:04
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    It's worth adding (from the cited Wp article) that "20 cwt referred to the weight of the barrel and breech". Commented Sep 23, 2023 at 7:29
  • @MarkMorganLloyd: Added. Commented Sep 23, 2023 at 11:09

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