.280 British

The British Army designed this cartridge after studying the German 7.92×33mm Kurz encountered during the Second World War, an intermediate round sized between a pistol cartridge and a full-power rifle round that let a shoulder-fired weapon fire automatically with controllable recoil. Britain set out to build its own intermediate round with a longer effective range than the Kurz, and paired it with a purpose-built rifle, the EM-2, alongside trials in the Lee-Enfield, the FN FAL and the Bren.

The round never reached service. Comparative testing against the American T65 cartridge at Aberdeen Proving Ground in 1950 went against it (the US Army held that the .280 British did not meet its requirements, citing accuracy and armour-piercing shortfalls), and a change of British government under Winston Churchill, who prioritised cartridge commonality within NATO, ended the programme. NATO standardised the American design as 7.62×51mm NATO instead.

No free dimensional standard exists for a cartridge that never reached production, so every figure in this entry is converted from the reference work Cartridges of the World and carries estimated status. No test-barrel length is published for either of its two loads, so only bullet mass is recorded for each.