It has to do with Russian military doctrine, as it relates to the European theater of operations.frankly I think the Russian only train their guys out to 400 even with the 545.
I can tell you that the round does run out of gas at 400+ yards. It still has the energy of a 9mm pistol at ~500 tho so it's not totally useless, you just have to depend on volume of fire rather than one shot stopping.