If a tank face an IFV which the rapid fire would inevitably touch the barrel, would tank be disabled regardless of its strong armor?
Possible but not necessarily. But to put it this way, if a tank turret is facing the IFV, the optics are a larger target than the gun barrel itself. Without optics an intact gun is useless as well. An IFV firing APDS or HE rounds can also disable the optics, tracks, sensors, countermeasures etc. It isn't difficult to mission kill a tank. Even a rifle round to the optica/sensors or a grenade to the tracks can mission kill a tank.
As with my previous message, no reasonable amount of armour on a gun barrel would stop an autocannon round.
If we taking into account newer hard and soft kills APS, a tank could possibly defeat the first few autocannon rounds before deploying further countermeasures and withdrawing or counterattacking.
I.e the laser defense system in the Type 99 tank would immediately blind the source of a lase and with hard kill systems would then deal with any incoming rounds as well as mark to location of the threat to the crew ready for counterattack.
But your arguement is valid. It certainly can happen. But the issues highlighted in my previous post do not go away.
The IFV crew must have big balls to choose to start an engagement with an MBT with autocannon and not an ATGM.