Re: Importance of staying supersonic at the target?
As suggested, it's a case-by-case question.
As bullets transition down through the transsonic threshhold, forces associated with the bullet's shockwave catch up with and traverse it's length from rear to front.
If the bullet's directional stability isn't still very well estabolished, these forces can introduce an upset in the bullet's directional alignment with the curve of the trajectory. Aerodynamically, this is no small change. This upset can introduce a directional deviation, pointed in a random directions shot to shot.
This increases dispersion from the point of transition. Depending on the bullet's underlying basic stability, this increase can be small, bigger, or huge. It is not inconceivable that the bullet may even switch ends, which we call keyholing. Imagine tapping a toy gyroscope in that instant when it starts to tip over. All bets are off.
Huge is relative.
Recognize that when a sight adjustment of 30MOA is dialed in to raise POI from a 100yd hit to a 1000yd hit, we're really only talking about 1/2 of one degree. 1/30th of that, 1MOA (at the shooter), alters 1000yd POI by 10". As distance to target deceases, this 1MOA deviation becomes smaller in actual linear deviation. Upsets can reach magnitudes of several, maybe several handfuls of, degrees.
The difference ontarget at 1000yd between going transsonic at 900yd, and not going transsonic at all can dictate missing by as much as several feet, or not much at all; depending on the bullet and the degree of stability the specific rifle and load imparts on it.
Greg
