From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Glaser Safety Slugs and other ammo
Organization: Lawrence Berkeley Laboratory

In article <36750@mimsy.umd.edu> n9020351@henson.cc.wwu.edu 
(James D. Del Vecchio) writes:
#decwrl!well.sf.ca.us!well!tmi@uunet.uu.net (Peter Kasler) writes:

##By far the best defense ammunition for 9 MM pistols is Winchester
##147-gr. JHP Subsonic. Next is probably Hydra-Shok 147-gr. JHP Subsonic.
##Avoid faster, lighter rounds, and absolutely stay away from Glaser 
##Safety Slugs and other frangible ammunition.

#Why?  What's wrong with magsafe 9mm for example (68 grains at 1850fps)?

I'm not familiar with the particular round you mention but I can make some
general comments.

Remember the FBI shootout in Miami?  Insufficient bullet penetration led to
the loss of several agent's lives.  Lightly constructed high-speed low-mass 
bullets just don't have very much penetration.  They tend to blow up on the
surface of the target.  This goes for rifle bullets as well as pistol bullets;
you'd be lucky to get an inch of penetration from a Hornet bullet out of a
Swift (if you could get the bullet out of the barrel without it turning into
a grey cloud).  You could flay all the hide off an aggressor with
multiple hits from some of these bullets but that wouldn't do the job you
wanted done in time to do you any good.  What you want is to stop the
guy, not torture him.

There are three ways in which these bullets can fail to achieve adequate 
penetration:
-One way is by expanding until there is too much frontal area for the small
bullet mass to push through the target medium.  Sort of like the feller
with the alligator mouth and the hummingbird behind.  
-A second way is via fragmentation - the bullet fails to stay together
and separates into small parts each of which has the same problem as 
mentioned in way #1.
-A third way is by having a bullet which is too light for its speed, even
if it's a non-expanding bullet.  This isn't seen too often but is possible.

All of these ways really boil down to the same fundamental thing - there is 
insufficient momentum in the projectile, or piece of projectile, to move all
the target-mass it must encounter.  Example: dust shot doesn't have any
penetration.  You know that, because of the laws of fluid dynamics, objects
which are light compared to their frontal area slow down fast.  You know
that, because of the geometric scaling laws of solids, similar objects
which are smaller have more frontal area per unit mass.  If you want more 
details on this subject, see my previous boring posts on momentum transfer.

Someone mentioned in a previous post that a bullet that holed a suspect
went on to kill an innocent bystander.  That's certainly a terrible thing
and is what drove manufacturers to make non-penetrating bullets.  But as
someone pointed out in an even early post, the vast majority of the bullets 
fired by the guys in the white hats (or blue, as the case may be) totally
miss their intended targets.  This kind of reduces the relative importance of 
the small number of overpenetrating rounds.  The upshot is that more white hats 
and innocent bystanders are saved by bullets that do their jobs, even if they 
overpenetrate sometimes, than are saved by non-penetrating bullets.


      JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Home defense weapon (WAS: 9mm Glock 17)
Organization: Lawrence Berkeley Laboratory

In article <37176@mimsy.umd.edu> gmk@falstaff.mae.cwru.edu 
(Geoff Kotzar) writes:

#I must confess to being confused about how the combination of bullet weight
#and velocity combine to produce soft tissue versus tactical penetration.
#The early light weight .38 SPL work seemed to indicate that light bullets
#and high velocities produced greater tactical penetration and reduced soft
#tissue penetration than heavier slower bullets. 
[........]
#Maybe someone out there has a reference to a systematic study of soft tissue
#and hard target penetration as a function of bullet weights, velocities,
#and constructions.  I would appreciate hearing about it.

I'm not much help on this, I'm afraid, but I can throw in two small facts 
regarding tactical penetration:
 
Hollow points turn into solids when they penetrate many materials because
their hollow noses get plugged.  Drywall (sheetrock) is a good example of
such a material.  The resultant solid bullet naturally has good tactical 
penetration.

Almost anything will go nicely through the sheet metal of a car door (not the
lock mechanism) because the thin sheet metal deforms into a cone which holds
the bullet together and keeps it from expanding.

          JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: auto glass deflection

While plinking at the range over the holidays, a friend and I stumbled
across various automobile windshields left behind by some inquisitive
gendarmes.  The windshields had huge unperforated areas so my friend
and I decided to conduct our own experiments.  We found no rhyme nor
reason to our results, but I though they might be worth presenting here
for comment.

The procedure was very simple.  A windshield was placed 7 yards from
the shooter so that a normal to its surface was at 45 degrees to the
line of fire.  A blank target was placed 90 inches behind the wind-
shield and, of course, its surface was at 90 degrees to the line of
fire.  Next, one piece of 3/4 inch square black tape was put on the
glass and another on the target such that the two squares of tape lined
up with the shooter.  A shot was fired at the two squares of tape and
when there was no deflection of the bullet from its path by the wind-
shield, both squares of tape were perforated.  At least 5 shots of each
species were fired.

We had the following rounds on hand: 45 ACP #68 H&G 200 gn LSWC @ approx.
900 fps, 45 ACP #4515 Hornady 200 gn JSWC @ approx. 900 fps, and a generic
357 mag 158 gn LSWC reload.  The results were that the #68 H&G went straight
through and perforated both squares.  The #4515 made two groups: one 1 to 2
inches from the target's square and one 4 inches from the target's square.
Both of these groups were deflected the opposite way you might think: the
bullets' paths were tipped _into_ the glass like light refracting when going
from air to glass.  The 357 mag 158 SWC went just the way you might think:
its path was deflected as if it had ricocheted ever so slightly on the
glass before penetrating it.  These bullets formed one group 4 inches
from the target's square tape.

So there you have it: one type of bullet went straight through, unde-
flected; one deflected to the right approximately 2.5 degrees and one
deflected to the left 2.5 degrees.  What does it all mean?  Who knows?

John Bercovitz     (JHBercovitz@lbl.gov)