Both r the same bro, actually the Soviets copied the Americans during the Vietnam war from captured M-16 rifles impressed they told Gen Kalashnikov to make a similar rifle round for the Russian army, though the Gen was not ready but he didn't have any choice..
Well the Soviets came with the with the AK-74 and further version..
It was known as the poison bullet,if hit for ex-the Mujahideen in Afghanistan,the part which the bullet struck had to be amputated.
The Americans complained this in the UN meeting and to ban the 5.45*39mm round,but the Soviets showed the middle finger to the Americans ..
But it's an intermediate bullet thus having its limitations, I would prefer the old M-43 old school round any given Sunday as it has great knockout power..
Even the Indian army realised this,but strictly believe we should have copied the RPD SAW with barrel change option &a belt version,and should have made our INSAS rifle by chambered 7.62*45mm Chzec round which was for the Chzec vz-52 a great round with more knockout power,thus activating a dead round to our own benefits...