From: gmk@falstaff.MAE.CWRU.EDU (Geoff Kotzar)
Subject: (null)
Organization: Case Western Reserve University

In article <51161@mimsy.umd.edu> gwyn@smoke.brl.mil (Doug Gwyn) writes:

     In article <50995@mimsy.umd.edu> gmk@falstaff.MAE.CWRU.EDU
     (Geoff Kotzar) writes:
     ##Does anyone know if the bullets used in the 10mm are the
     ##same as the .40 S&W? Has anyone sectioned any of them?

#Of the 18 different .40S&W factory ammo samples in my collection,
#there are 16 distinct bullet designs.  While it is possible that a
#given manufacturer may be using the same bullet for both .40S&W
#and 10mm, certainly there is enough variation among manufacturers
#that attributing poor full-load 10mm performance to bullet sharing
#between .40S&W and 10mm ammo products would be simplistic.

The reason I asked about the particular bullets used in the two cartridges
is that the 10mm was developed first and some of the bullets that are
currently available in factory rounds may reflect the original design
parameters. The bullet designs may not have been revised to bring their
performance into agreement with continually evolving criteria. The bullets
that are now available for other older cartridges reflect 20 to 30 years of
development. The wonderful Hornady XTP's have gone through at least three
distinct design revisions over the last two decades, and Speer's flying ash-
tray (.451 200 JHP) was not always what you see. And yet they ALL were
supposed to deliver the kind of performance that we now come to expect in
ALL of their previous incarnations. It just wasn't so.

My points in the above are two: first, I suspect that the bullet(s) used in
the 10mm are not the same as those loaded in the .40; and second, that it
takes time for the designers to match their designs to the performance goals
given the constraints placed upon them by the manufacturing methods their
companies employ and the (possibly) continually changing design specifications.
If the bullets used in the two cartridges are different then we would be
talking about two different DESIGNS rather than the same design operating
under different CONDITIONS.

#I don't know why anyone would be surprised that, under circumstances
#where a 180 grain projectile at a speed of 1000 fps penetrates just
#about optimally, a 180 grain projectile at, say, 1500 fps would
#penetrate too far.

In fact I would be somewhat surprised if what you say were true in general.
My reason for saying that is for a handgun projectile 500 fps is a substantial
velocity differential and it is not unusual for the velocity envelope for
proper performance of an expanding bullet to be smaller than that. For non-
expanding bullets it is true that increasing velocity will increase penetra-
tion, not necessarily in proportion to the velocity increase but it will be
increased. For expanding bullets, the situation is different and it is a func-
tion of the velocity. At velocities below which expansion occurs, JHP's act
like slow FMJ's. As the velocity is increased to the design level -what ever
that may be- the bullet expands, holds together, and penetrates well. Over
drive it and expansion becomes excessive and pentration suffers. This is in
fact what Martin Fackler (and Peter Kasler here on the net) has been saying
for some time. This happens all the time in the hunting fields so it is
nothing new. I think it only seems new to people who keep handguns for defense
because they do not see the rounds interact with tissue much. I know from
personal experience that the fragile Speer 200 JHP .45 ACP factory load
will not expand on medium sized canines and yet the much more heavily con-
structed 260 JHP .45 for the .45 Colt when driven at at the extremes of its
allowable velocities -1600 fps in a .454 Casull- will expand so suddenly and
violently that it will cut a jackrabbit in two, literally.

I admit that when a bullet is driven too fast what happens can take a number
of different lines. If it expands TOO much and holds together then penetra-
tion will usually be less than optimal; if it comes apart totally then, again,
pentration will be shallow. If on the other hand only the nose blows off and
what remains is sizable enough it can continue penetrating deeper than if it
had held together. This is the principle of the Nosler partition rifle bullets.

I recognise that the above paragraph represents an extreme set of conditions
and that it jumped over those that may apply in the case of the 10mm. As
velocity increases but stays below the fragmentation range for the given
projectile, expansion and penetration can both increase simultaneously. But
to determination the point at which penetration falls off as expansion in-
creased would require some experiments to determine the chain of events as
functions of velocity. And then it would only apply to the bullet tested.

#I think major ammo manufacturers generally test each ballistic
#package and adjust the bullet design, velocity, etc. for good
#performance.

I do not doubt that they do test their designs but "good performance" is
somewhat subjective. In one of his articles in Handgun Quarterly on the FBI
tests, Charles Petty recounted that once the FBI had specified bullet weight,
velocity, expanded diameter and pentration depth the ammo manufacturers
finally had an objective set of criteria to design with. It is very hard for
the ammo designers to know a priori what constitutes proper performance in
a defensive situation. Look at it another way, the people who make the ammo
are not gunfighters. The FBI set the specs which resulted in the 9mm 147 JHP
sub-sonic round appearing superior and it is not living up to expectations.
The FBI has a large body of information concerning gunfight statistics,
some of it first hand and they still are not able to set performance speci-
fications that are meaningful. Ammo manufacturers have objective criteria
when they deal with muzzle velocity, velocity variation, accuracy, feeding
reliability, ect; even expansion and penetration are or can be objective but
then they have to ask the question "how much is appropriate for a given appli-
cations". This is where the problem crops up.


geoff kotzar          gmk@falstaff.mae.cwru.edu