any pictures or specs or the caliber of that thing? iv never heard of it, but iv never really researched Japanese weapons. oh yeah, by "most powerful" do you mean muzzle energy? or caliber? or amount of propellant?
Some thing big and nasty that would keep the enemy well back from the trenches. Who wants to shoot some one with a rifle when some else can do it with a large chunk of artillery, the further they are away from me the less chance of me getting hit.