April 2026 (2) - Flipbook - Page 41
drag is frequently underestimated by 2–5%, leading to potential
errors in long-range trajectory
calculations.
Bullets traveling at Mach 0.8 or
slower encounter stability issues
primarily because they have entered or passed through the transonic range (roughly Mach 0.8 to
Mach 1.2), where aerodynamic
forces shift signi昀椀cantly.
At these speeds, the following
factors compromise 昀氀ight stability:
• Center of Pressure (CP) Shift:
As a bullet slows into the transonic region, the center of pressure—where aerodynamic forces
act—shifts forward. If the CP
moves too far ahead of the Center
of Gravity (CG), the “overturning
moment” increases, making the
bullet prone to pitching, yawing,
or tumbling.
• Base Drag and Air昀氀ow Detachment: For boat-tail bullets, the
air昀氀ow often detaches from the
tapered base as it drops below
Mach 0.9. This creates a turbulent wake that can “bu昀昀et” the
tail, leading to erratic movement.
Flat-base bullets are typically less
a昀昀ected by this speci昀椀c issue.
• Magnus Moment: Changes in
the air昀氀ow around the bullet base
can trigger the Magnus moment
(not to be confused with the
Magnus e昀昀ect), which destabilizes the projectile’s spin and can
lead to dynamic instability even
if gyroscopic stability remains
high. This is The Phase inception
point. Where our bullets are very
susceptible to odd wind or condition abnormalities often due to
range topographical anomalies or
strange wind sheers.
God bless Black Powder!
• Dynamic vs. Gyroscopic Stability: While a bullet’s spin (RPM)
decays much slower than its
forward velocity—meaning its
gyroscopic stability factor (SG)
often increases as it slows—its
dynamic stability decreases due
to the shifting aerodynamic loads
mentioned above.
• 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 “shotto-shot” drag variation, leading
to poor accuracy at long ranges.
This pertains mostly to modern
boat tail bullets. As our 昀氀at base
bullets are much more stable in
the transonic range of speed.
So we of course strive for breaking perfection in shot let o昀昀. To
avoid any tipping at the muzzle.
That’s a given. The need for a
perfect let o昀昀 and proper follow
through, is critical.
Something I that took away
from Volume 1 page 29 of Litz’s
Modern Advancements in Long
Range Shooting: “just because
the groups you’re shooting are
good, doesn’t mean that your
bullet is 昀氀ying with the best possible BC!” This explains much!
While my 93.5 gr load shot well
at the ranch in 2024, @ the150th
Creedmoor Anniversary match.
My 88.5 gr load has a much higher BC.
sary Match in 2024.
Something of an Eye opener!!!!
This keys into exactly what I am
discovering now, while conducting these tests with the labradar
unit.
There are a good many folks
complaining about the labradar’s
set up time, I read about. I 昀椀nd
it not nearly as time consuming
and tedious, as my old Ohler 35P
Chronograph setup! Something
interesting is that the radar unit
Bryan Litz uses, it is made by the
same company that makes the
labradar unit from Canada. I 昀椀nd
that rather interesting, actually damn interesting! While the
labradar lacks the pure Doppler
power of the Litz unit it gives us
much material and data to work
with.
This of course is an ongoing
study. There are two signi昀椀cant
take aways to this study to date.
We need to make as perfect a 昀氀at
base bullet as we can, and using
faster barrel twist will help in
maintaining down range stability. The use of the labradar, which
gives the individual their own
personal Ballistics lab. When
used to maximize their bullet’s
Ballistic Coe昀케cient, and maximize their long range experience.
The quest for answers and accuracy continues.
Kenny Wasserburger
My 89.5 gr load used at Baker
MT shot quite well in June and
August of 2025 also. It also has
a signi昀椀cantly higher starting BC
than the 93.5 gr load, that I used
in the 150th Creedmoor Anniver-
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