Fwd: Fascinating ballistics discussion from rec.guns

# Somewhere in the last set of responses I received there was a pointer
to an
# FBI document discussing handgun wound characteristics. I had actually
read
# that before, but the pointer provided a good reminder that the
document
# should be read, re-read and understood.
#
# If you buy the argument (do you?) that there is no such thing as
"stopping
# power" or "knockdown power," what would be the difference between 9mm
and
# .357 Mag if the same or very similar bullets were driven at the same
# velocity? I think 9mm is about .356 and .357 is obvious, so the cross
# sectional area is the same. If they are loaded to the same velocity
(and I
# think Corbon produces loads with very similar velocities) I would
expect
# both penetration and projectile expansion to be roughly equal;
consequently
# the crush cavities would be similar, as would the probability of
penetration
# to a vital organ.
#
# If all of that is true and you buy the claim that the .357Mag is an
adequate
# self defense caliber when properly loaded, doesn't that imply that the
9mm
# has to be adequate also. And what about .38 Special +P or +P+? Why is
the
# 9mm failing in Iraq then? .45 ACP Corbons seem to have the same
penetration,
# obviously larger cross-sectional area-- but still, you're depending on
blood
# loss to incapacitate if the FBI is right. Are the 9mm NATO rounds not
# penetrating?
#
# Also, since blood loss caused by the crush cavity is the main cause of
# incapacitation (unless the brain or upper spine is hit) the all
important
# second and third shots enters as a factor.
#
# I've always considered the .45 ACP, 9mm, .357 Mag about equally easy
to
# shoot. Maybe I should do some testing and see which allows me to be
back on
# target for the followup soonest. I'm certain it will be fractions of a
# second difference, but one might be easier to recover from than the
other.
#
# I think the difference might be too small for a stopwatch. Any ideas
how to
# measure?
#

9x19, .357 Magnum, .38 Special are of course essentially the
same diameter bullet. The differences in terminal
performance arise generally in bullet weight, velocity,
mechanical design, and penetration differences.

A .357 Magnum can push a 158 grain or 180 grain JHP or JSP
at a velocity that offers a higher probability of deeper
penetration. However, as long as a bullet passes the FBI
and/or IWBA testing protocols with tissue penetration of at
least 12" and decent expansion, then it is considered
adequate for self defense handgun engagements.

If a 158 or 180 grain can do this, then they are fine from
that perspective. But these two loads also generally have a
higher potential for over-penetration in tissue, which can
pose a higher hazard to immediate bystanders. And just
because a bullet runs faster and or is heavier, it does not
necessarily mean that the bullet will expand reliably. That
still varies, depending on the mechanical design of the bullet.

Modern quality 9x19 JHP designs exhibit robust expansion and
they penetrate to or past 12" in tissue simulant (as do .45,
etc.). This also has been well correlated in forensic
pathology studies. The best known on the web is that
conducted by Eugene Wolberg of the San Diego PD. As of his
passing, he had compiled about 150 OIS incidents in an
ongoing study where he compared the autopsy and forensic
results to tests in ballistic gelatin and found a very good
correlation of penetration and expansion.

In fact, if you compare a good 9x19 to a light .357 Magnum,
their terminal performance is close, with the .357 probably
penetrating and/or expanding somewhat more. However, light
fast bullets often have difficulty with barrier penetration
such as windshields and they can fragment more frequently
(in handgun ammunition, not considered a good thing). So if
you combine this with the tactical advantages of
semi-automatic pistols, this has contributed to the .357
Magnum losing favor as a service/duty load. But if you feel
you really need some extra penetration for defense or trail
use, and over-penetration is not an issue, there is no
reason why a good quality .357 Magnum load would not work.

In regards to .38 Special, this caliber historically has had
difficulty in providing a bullet design that could both
reliably expand and penetrate to 12", especially from
snubbies/BUGs, which is a common application for this
caliber. In the past few years, Speer has done a good job of
designing a Gold Dot Short Barrel load, which because of its
mechanical design, works better at the slower .38 velocity
window.

As to 9x19mm terminal performance in military applications,
there is no controversy with penetration. Both 9x19mm and
..45ACP ball penetrate well, especially when against
non-armored opponents. Keep in mind though that the military
is limited to using full metal jacket (ball) handgun ammo
(or AP also), which is not designed to expand. As a result,
the 9mm can only produce a roughly .357 hole, as opposed to
a .45 ACP for example. Though that extra diameter may allow
for a higher potential to damage vital anatomical
structures, and the extra mass may allow for better barrier
penetration in some instances, there a numerous trade offs,
such as magazine capacity and platform handling
characteristics, which tactically can offset individual
wounding effects of 9mm vs. 45ACP ball projectiles.

As to stopping power, *provided* people treat and view it in
context as a general, colloquial term, then I don't have a
real big objection. But especially as regards comparing
handgun service calibers, I do strongly object to claims
that this or that round is the shiznit because of some
"stopping power" or "one-shot-stop" stat read somewhere.

There are so many variables involved that, even with loads
exhibiting good terminal performance, trying to correlate
and quantify an actual, meaningful, comparative "stopping
effect" is extremely problematic. This is especially at
issue if you try to predict on the basis of statistics,
where the raw data may not have been published, where data
collection, statistical analysis or methodology may be
seriously flawed; where there is no sound evaluation of the
data points in context with the actual shooting incident
reports and autopsy/trauma reports, no demonstrated
physiological links, etc.

As to a method of measuring target re-engagement speeds, the
only method I could suggest is high speed video. However, I
don't think any re-engagement advantages by caliber are
likely to make a difference in practical terms. Within
reason, I think the platform characteristics and the
training/ability of the shooter are going to be far more
important.
--
Peace, Om

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"My mother never saw the irony in calling me a Son of a bitch" -- Jack Nicholson
.