With armor ever going thicker, and composite material getting stronger each year, it would be natural that you start to field better and bigger guns.
I read from some where that the us army was trying to knock down some crippled tank in Iraq, and using the 120mm gun from the M1 and it did not penetrate. So if one day China's army had to face a tank like M1 then they better have a better and bigger gun, so they have a chance to penetrate the armor.
That incident you heard was US army trying to destroy one of their own disabled tank with another. They fired shots against it but could not cause any damage that would ensure no technical secret could be gained from it. So they had to set up explosives to finish it off. But that tank was out of commission from a combat capable standpoint after the first shot.