I am a retired Science teacher. It took me 30 years to get out of the 8th grade, but I finally graduated. During that time, I taught a mixture of Biology, and Astronomy, and Physics, and Chemistry, and Earth Science.
All rifle barrels vibrate like a tuning fork. A shorter tuning fork vibrates at a higher frequency.
The following explanation came from a guy who was a mechanical engineer (cannot remember his name at present) and a rifle accuracy nut. His explanation found below made sense to me.
The ideal situation is when the bullet exits at the point in the cycle when the muzzle is vibrating in the upward direction. A slightly faster bullet exits lower in the upward cycle. A slightly slower bullet exits slightly higher in the cycle producing a slightly higher launch angle, which ends up putting the bullet at the same place on the target. This would produce "nodes".
If anyone here has another explanation or can correct the one above, I will not be offended. It is the way science is supposed to work.
