How Does Distance and/or Velocity Affect Ballistic Neck?

[Gumier6]

Let's say a M855 round fired into ballistic gel has a neck (distance between entry and beginning of larger gel disruption AKA tumbling/fragmenting) of 6''. Will decreasing the velocity (or increasing the distance to the gel block) increase the length of the neck? Or will the bullet start to get unstable and the neck will decrease?

For example, let's say we move the gel block another 200 yards away. Will the neck be more like 4'' or 8''? My thinking is that as distance increases/velocity decreases the neck lengthens to the point the bullet no longer tumbles/fragments and acts in more of an "ice pick" manner. Am I correct in thinking this?

[gaijin]

From experience I would say you are correct in your assumption.
Also, from experience, I believe you would need to test the assumption to prove it.