Hello. I read that three configurations were studied for the 447. One is the one seen in models: gunner and commander on the left side of the tower. But the final configuration was classic. Just like other contemporary case: Leclerc.
Furthermore, the unified ammunition was finally chosen. Projectiles almost two meters long. Does not look like they may have been accommodated in this model and be introduced into the gun. The breech is far behind.
According to this picture:
the barrel does not seem external. Which coincides.
Now, joining all these elements, and considering the object 450, the same bureau.
It is speculation but ...
Flacon turret style, or maybe Black Eagle turret style, whit few rounds ready; very long unitary ammo.
What do you think?