Do any other countries produce 152mm shells? It would be a massive money maker for them right now.
AFAIK Russia is the only country that still uses 152.4 mm (converted from 6 inches) ammo. No other country does except maybe Belarus. The rest of the world uses 155 mm. 6 inches ammo dates to before WW1 at which time Russia imported it from Britain and adopted 6 inch gun.