If you look at the length comparison in those images the APFSDS rounds and their propellent booster charges look about 2.5 times longer than the standard propellant stub, but standard 125mm rounds are about the same size as the propellant stub... HE-FS and HEAT-FS and APFSDS...
So the long APFSDS rounds might reach the floor but traditionally a Russian tank only carries a small number of APFSDS rounds and the vast majority are HE Frag FS shells and HEAT-FS shells... which could have inert blocks positioned underneath them in this autoloader tube in case of a mine going off.
So the long APFSDS rounds might reach the floor but traditionally a Russian tank only carries a small number of APFSDS rounds and the vast majority are HE Frag FS shells and HEAT-FS shells... which could have inert blocks positioned underneath them in this autoloader tube in case of a mine going off.