The Russian ammo is separate: In the T-72 and T-90, each propellant charge sits above it's projectile in a cradle which is elevated to the ramming position. The shell is rammed, then the cradle drops down a level and the charge is rammed. In the T-80, the two components are gathered up by a cradle and them rammed in one action.
I think you very probably could use a human loader with the 125mm.
I've encountered a claim online stating that the EE-T2 Osorio MBT uses a version of Vickers Mk.7 turret and was to have a version armed with a Eastern-Bloc standard 125mm gun.
Hum...... export Challenger or maybe even Iranian development of Chieftain with Ukrainian or Chinese 125mm gun......?
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Also, from Wikipedia page for Mobarez, actual Iranian development of Chieftain:
The gear box is changed so the tank can have 360 degrees turret turn.
Huh? Does Chieftain tank have some problem with turret traverse?