Tank Gun Autoloaders & Ready Rounds

[Marcello]

It would seem that, barring a secret autoreloader or undisclosed fourth crewman, once the carousel is empty the main gun is basically down until it lays up for a while in a quiet spot away from the action (say, a supply point?)

No, AFAIK at least on the T-XX you can load directly from the racks without refilling the autoloader. It is slow (one round per minute, less with a well trained crew but still slow), awkward and it will distract the gunner and commander from others tasks, but certainly doable if you are, say tossing HE to support infantry. Dunno the Leclerc and the others vehicles.