[norton]

Sitting here on the edge of dotage I can't remember the mark or number that changed but the UK SMLE had a semi detachable magazine with a cut off allowing for single shot use well into the 20th century. The idea was that multiple rounds were a reserve for use only when authorized and in dire straits.

Also, IIRC (see above at "dotage"), US infantry in the Spanish American war were still carrying black powder trap doors. Cavalry, Rough Riders and Buffalo Soldiers, were armed with new, smokeless, 30-40 Krags at Kettle/San Juan hill.
Oh, and Gatling Guns.

[M1903A1]

The SMLE lost its magazine cutoff (along with a bunch of other outdated features like “volley sights”) in 1916. I think the model was the No. 1 Mk III*.

Back home in the States, 1903 Springfield rifles continued to sport a cutoff right to the end of production in 1944-45.