Re: " node "
It has to do with barrel vibrations. When the gun is fired, the barrel vibrates, and the tip of the barrel moves, influencing the direction of the bullet as it exits the barrel. When the barrel reaches the extent of its travel, it momentarily is motionless. Similarly, just before and after the node, the acceleration and deceleration are minimal. Theory has it that the bullets will group closely on target due to the minimized barrel tip movement. A good load will have your bullets exiting each time when the barrel is relatively motionless.
The term NOde means that NOthing is happening.