The next version of Russia's T14 Armata main battle tank will be armed with a previously rumored 152mm gun.
The 152 mm tank gun could penetrate 1 meter of armor.
For 11 years, China has been testing a 140mm gun on one its Type 98 tanks. The 140mm gun could fire an armor piercing round with twice the penetrating power of one fired from a 120mm gun (about 22 mega joules of energy, versus 11), the amount of ammunition carried was reduced by about a third (to 20-30 rounds, depending on the tank). The 140mm shell was about fifty percent larger than the 120mm one, and could probably knock out an M-1 tank with a frontal shot.
When the Armata (T-14) tank gets the 152mm gun, it will be the most powerful cannon to be mounted on a main battle tank of any country ever.
The unmanned remote-controlled turrets of T-14 tanks that rolled on the Red Square in Moscow on Victory Day, May 9, were armed with a brand new 125mm 2A82-1M smoothbore cannon with improved accuracy and angular dispersion.
SOURCES -UA today, Wikipedia