April 2026 (2) - Flipbook - Page 35
• The “Gray Zone” of Stability:
Bullets with an SG between 1.0
and 1.5 are considered “marginally stable.” At Mach 0.8, these
bullets often exhibit increased
pitching and yawing, which
drastically reduces their Ballistic Coe昀케cient (BC) and causes
“shot-to-shot” drag variation,
leading to poor accuracy at long
ranges.
Further discussion on the mechanics of this Phenomenon.
Bryan Litz, a well-known ballistician and founder of Applied
Ballistics, considers the transition from transonic to subsonic
昀氀ight to be the greatest challenge
in extreme long-range shooting.
I have a modicum of experience
in this area with our mile Match.
It may behoove a few to crack a
book occasionally, and expand
your knowledge base. This transition occurs roughly between
Mach 1.2 and Mach 0.75, with
signi昀椀cant e昀昀ects typically starting around Mach 1.2 (approximately 1340 fps). Remember
this is for modern BOAT TAIL
bullets. For our 昀氀at based bullets
it’s right around 900 fps. Which
interestingly enough, help with
their transition from transonic to
subsonic speed. See below.
Key Points from Bryan Litz
Instability and BC Loss: As a
bullet enters the transonic zone,
it can lose stability due to changes in shock wave and turbulence
patterns. This instability manifests as pitching and yawing,
which dramatically increases
drag and consequently degrades
the bullet’s ballistic coe昀케cient
(BC).
Twist Rate is Crucial: A faster
God bless Black Powder!
barrel twist rate can improve
stability in the transonic zone by
suppressing yaw to a negligible
level and maintaining a higher
BC. Litz’s research indicates that
using a slightly faster twist rate
generally helps with transonic
stability and usually does not
hurt precision (group size).
Bryan Litz has published his
extensive research and 昀椀ndings
in his books, such as Modern
Advancements in Long Range
Shooting and Applied Ballistics
for Long Range Shooting. He also
discusses these topics in detail
on his podcast, The Science of
Accuracy.
Bullet Design Factors:
Shorter bullets with shallow
boat-tails or 昀氀at bases tend to
perform better through the transonic transition. Considering that
our bullets live in the Transonic
range until right at around 900
yards. Note the mention of Flat
Base bullets!
Now keep in mind as I stated
above just past the muzzle, our
bullets live almost entirely in
the transonic range to right at
900 yards. What I call the Phase
inception Point. Or the Magnus
Moment. Now I know some folks
think I was just seeing things, but
it is a actual physical reality.
Bullets that are very long for
their weight are more susceptible
to transonic instability.
Logically one would 昀椀rst start
at the point where your velocity
would maximize your particular
bullet’s BC. That’s sort of a no
brainer in my book. That would
be the 昀椀rst step in mitigating the
e昀昀ects of the Phase Inception
Point upon your bullet’s trajectory. You know, that imaginary
nemesis of mine, at around 900
yards that occasionally shows up,
to mess with one’s bullet but not
always.
Environmental Factors: Air density (driven by altitude, temperature, and atmospheric pressure)
plays a signi昀椀cant role. A bullet
that is stable in the thinner,
high-altitude air might become
unstable in the denser air at sea
level when it slows to transonic
speeds.
Predictability is Di昀케cult: Transonic stability is hard to predict
with formulas alone and often
requires extensive live-昀椀re testing across various environmental
conditions and twist rates.
Modeling for Accuracy: To
achieve 昀椀rst-round hits when
shooting into transonic ranges,
Litz emphasizes using a ballistic
solver capable of running Custom Drag Models (CDMs), which
are derived from actual live-昀椀re
data and more accurately represent a speci昀椀c bullet’s drag curve
through the transonic range than
generic G1 or G7 models.
At 900 yards to be on target one
must have approximately 16-18
MOA more elevation than what
was used at 800. To be on target
@900 one’s bullet is approximately 12-13.5 feet above the 800
yard target. Maybe a study of the
昀氀ag pole @800 yards could be
useful. If we maximize the BC of
our choice of bullet, we theoretically should lessen the chances of
yaw and defections @900 yards.
This of course is theoretical currently, but it is something worth
looking into.
The increased twist rate, is
perhaps the best method at
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