IMO, likely a copy of the 76 mm D-56T used in the PT-76 amphib tank. The auto loader technology could have came from the KBP 2A28 Grom (73mm), which is fitted to the BMP-1, which is again, in Vietnamese service.3 indigenous armoured vehicles for Vietnam Army. The T-01 is the light tank prototype using 76mm gun but with auto loader.
Ukraine War shown the thinking to retain calibers of what can be supported by your most produce or stocks ammo is workable. Reverse engineer what already has, also less needed foreign design/production license.The Vietnamese approach has been to copy what they have in service as it is what they know works, and also to retain calibres which they already have plenty of stock ammunition, and less about whether the technology is "better" or obsolete.


Nearly everyone use this approach. It is just China manage to bring their RnD commitment with the help of their large Industrial base. Puting the money and RnD effort also shown the big progress with Turkiye. Whether anyone else able to achieve this strategy depends also on their bureaucratic environment. India is big example on that, despite tons of money and RnD effort being push to it. They have strong RnD base but seems being slown down by Bureaucracy and Inter Government rivalry. Don't get it wrong, they have achieve far, but should be done better base on their resources.Our approach is similar to China’sin the past , copying available weapon models and purchasing production licenses. In the next 10 years, you will see us advancing even further in the defense industry.
It's interesting, the XCB-01 I saw photos of before had a different turret shape. This one looks more like a typical BMP-1 turret.View attachment 54766
3 indigenous armoured vehicles for Vietnam Army. The T-01 is the light tank prototype using 76mm gun but with auto loader.