Case Head Failure in Semi-Automatic Handguns

	Looking through the Newsgroups I see references to semi-automatics
blowing up, (specifically Glocks) but there never seems to be any 
details or lessons learned from these incidents.  In the following 
text I will describe my experience with a case head failure, what 
caused it and how to prevent it from happening.

        I personally don't believe any of the Glocks talked about in 
the Newsgroups blew up. What I believe is that they are case head 
failures and nothing more.  This can happen to any semi-automatic 
but, the Glock being made with a slightly larger chamber can cause 
the brass to stretch more than normal, which in itself is no problem, 
but when this brass is re-sized and reloaded several times it is a 
definite problem.  I personally like Glocks and don't mean to knock 
them, but anyone reloading for them or any other semi-automatic 
ammunition must realize they're shortcomings to reload safely.  

	In talking to Glock I found that they size all their 
chambers to the upper end of the SAAMI specifications to make sure 
they will feed any ammunition.
        
        When reading reloading manuals a lot of attention is made 
to case head failures in rifle ammunition which has a different 
failure mode than semi-automatic ammunition.  This leaves the 
average reloader thinking they know what to watch out for when 
reloading handgun ammunition.  My experience with a case head 
failure in a Glock was relatively uneventful, it just blew the 
extractor off the slide and blew the bottom off my magazine 
leaving me with a hand full of bullets! 

This is not something you want to happen in a self defense 
situation, it could be down right embarrassing!!!  

When I talked to Glock with the intent of ordering a new extractor, 
the person I talked to immediately asked if I had a case head failure,
I said yes and he offered to send a replacement extractor free 
of charge.

        The magazine base plate was a glock+2 (Which in 
a .40 S&W is actually a Glock+1) which is made of a flexible 
plastic construction allowing it to pop off the magazine 
without damaging the rails at the magazine bottom, 
so no problem there. As easy as the Glock+2 add on can be 
popped off, especially with a fully compressed magazine spring, I 
think anybody that uses one for defense purposes is nuts.
Therefore I have retired it to the sounds good but doesn't 
really work pile. 

I received a burn on the back of my right 
index finger that was so slight I did not notice it for 
a couple of days.  The brass case was in three pieces 
but the extractor is the only item that went sailing.

        Before I was going to do any more shooting with that 
brass (or that gun for that matter) I wanted to do some real 
investigating to find out what the cause was, and how to prevent 
it from happening again.

        I unloaded all the remaining brass and started 
inspecting the remains of the failed one. having all the pieces 
was great because it showed me just where it split. with 
this as a starting point I examined all the remaining brass.  
What I found is that one third of the brass I was using was 
in the advanced stages of head separation.  Where I screwed 
up is buying used brass for a semi-automatic.
This brass was purchased from one of the well known reloading 
parts catalog houses, so where you get it doesn't really matter. 

        Enough for the history, This is what I found.  
The repeated working of the brass from firing and re-sizing 
causes the brass to crack in a ring around the head, the 
problem is that the cracking starts from the inside of the 
base and nothing can be seen from the outside until the 
really advanced stages where it will almost separate 
and the base bulges on the 
side walls near the case head.  The crack does not travel to 
the sides of the case but rather travels straight down 
to the extractor groove.  With the dark inside of the 
case it is really hard to identify the early stages of 
separation.  To complicate the situation, in the brass 
manufacturing process rings and other imperfections 
are impressed into the inside of the case head,  these 
rings can look very similar to the early stages of case 
head separation and vary from manufacturer to manufacturer. 

        The best tool that I have found to view the area 
that cracking starts is an OPTHALMOSCOPE.  This is the 
gadget the eye doctors use to look inside your eye. It 
is a magnifying glass with a selection of lenses and 
a light, that is right in line with the lens so there 
are no shadows from the brass case sides. It works great.

	  I know of one other person that had a case head 
failure.  It was as a result of re-manufactured ammunition 
with an apparent double charge.  It did a considerable 
amount of damage to the inside of the Sig. but there 
was no injury to the shooter.  Visually the brass looked 
the same, but it took some work to extract it from 
the barrel.

	I have been looking at mixed range brass that I 
have collected for the last few years and have found 
that the majority show signs of cracking. Here are 
some numbers to show what I have found.
 
	         brass
cal.  		good 	cracked 	percent cracked
.380		8	8			50
9mm Lug.	18	72			80
.40 S&W		30	131			81
.45 Auto	30	19			39

	It is obvious that the .45 is a low pressure round.  
If the others were loaded to a target velocity 
there would probably be a higher percentage of 
good brass.
	The majority had small cracks and quite possibly 
could have been reloaded again, but without knowing 
just how deep the cracking had gone I am considering 
them bad and I would not use them.

        As for possible ways to reduce the working of the 
case, and extend the case life, my first approach will be 
to size the front half of the case only.  this should 
hold the bullet firmly but not work the metal in the 
critical area where cracking occurs.  I haven't 
tried this yet and will add a paragraph when I have some 
information. The next step is to load for target velocities
whenever possible.

	After using new brass I have found that on the first 
firing the majority of the brass shows a slight crack, but 
on the second firing the crack does not seem to grow very much.  
I have no way of determining how deep the cracks are going, 
so I will shoot this same set of brass to see how the width 
of the cracking progresses. I am using a mix of brass for 
this test and the Winchester brass is holding up the best. 
I am loading for target velocities of 750 F/S (3.5 grains 
of Red Dot) with 180 GN bullets and only sizing the front 
half of the case.