Quoted:
Before WWII there was A LOT of testing of .270 caliber rounds in England. There was some testing and development in the U.S. as well. It was all dropped due to the war for obvious reasons.
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Actually the British started testing a .276 cal mauser action to replace the incomparable No1 MkIII SMLE in 1910, with development stopping due to the outbreak of ww1. They ended up sticking to the .303, simplifying the SMLE somewhat, and shipping the mauser tooling (converted to .303) to the US. We produced these rifles as the P14 for british home service use until 1917 when we finally decided to get in on the fun. The Springfield was in short supply, so the P14 was converted again to 30-'06 and renamed the M1917 Enfield for american use. More of these saw service than Springfields, IIRC.
The Canadians actually fielded a .280cal cartridge in their misbegotten son of a sewerpipe, the Ross rifle (later also in .303), though one too many jammed or blew their bolts back at their users and the canadians switched over to the SMLE also.
No, there won't be a test on this, though if you REALLY want a story, check out the US produced, never-exported, and service-issued Mosin Nagants for a good time.