How does it aim at a moving target so that it can fire an APFSDS round? It does not seem to have the mechanism to track by slewing.
I think it is meant to be fitted onto a turret operationally. The current towed arrangement is only for display and transport purposes. The fact that it is meant to fire anti tank weapons like APFSDS makes says to me that it is definitely meant to be put on a turret.
---
Anyway, L/55 120mm gun is 6.6m long, which doesn't seem too far from the gun we see here. The increased barrel length compared to L/44 while retaining same internal geometry and same ammo can increase maximum range (by 1.5km), higher peak pressure and higher muzzle velocity.
The presence of single round APFSDS for this 125mm gun as opposed to two piece rounds in carousel autoloaders of older guns makes me think that if/when it is adopted by PLA, we may end up seeing a bustle autoloader (which can use single piece rounds). Single piece rounds have longer rods, which translates to greater penetrating power.
A 125mm round versus a 120mm round also means more propellant. A longer gun means more range and more muzzle velocity. All in all the claim that the 127th institute's claim that this is the world's most powerful gun of this type could have some merit, depending on the type of ammunition used.