From: knapper@bga.com (Woodrow W. Baker)
Newsgroups: alt.engr.explosives
Subject: Re: 20mm. shell.
Date: 14 Sep 1995 13:06:44 GMT

I can't tell you a whole lot, but I have been working with a project that
involves 20 mm shells.  Raufoss (a norwegian company I think) invented a 
non-fuzed, high-explosive incendiary semi-armor piercing technology, that 
they sell world wide.  They have published brochures on it.  The U.S. 
licenced the technology, and currently uses it on a number of diffrent 
rounds.  There is a basic patent that covers the technology, and you can
obtain a copy of it from the patent office.  So what follows is based on
that patent.

The shell in question consists of a hardened steel body, (which acts as a
armor piercing body), and a deformable nose cone.  The body is packed
with a high explosive (typicaly A-4 though it can be others as well).
There is a second layer of a very hot incendiary pressed in on top of the
explosive.  This layer has a small hole or depression in it.  There is a
steel disk with a small hole in it that fits over this.  The nose is
filled with another incendiary, that ignites easier.  It is pressed in
with diffrent densities.  The entire nose is then pressed into the body.
This round is speced to go off with impact on .080 aluminum.  When the
round hits, the nose (soft aluminum) deforms, and that action is enough
to pinch the incindiary, and transfers enough heat and energy to start an
ignition.  The incindiary burns through until it hits the steel disk
(used to provide support for the nose incindiary against set-back
forces).  The hole in the disk allows a jet of flame to ignite a large
area of the incindiary over the exploseive.  As that burns, it generates
enough heat and pressure to cause the HE to go from deflagration into
detonation.

The body then explodes into fragments.  So you get a fireball within some
inches of penetration, and then an explosion within another few inches or
so.  It generates a number of fragments that do a *lot* of damage as they
continue to move forward in a cone shape.

Further details I can't talk about.

Cheers
Woody


--
Woody Baker Postscript consultant/ hired software gun /flintknapper
knapper@bga.com        woody@knapper.cactus.org
"If you ain't bleedin' you ain't knappin'" -->go ahead, ask me!

-------

From: arno@utu.fi (Arno Hahma)
Subject: Re: 20mm. shell.
Organization: University of Turku
Date: Sat, 16 Sep 1995 18:14:26 GMT

In article <4399d4$bme@giga.bga.com>, Woodrow W. Baker <knapper@bga.com> wrote:

>involves 20 mm shells.  Raufoss (a norwegian company I think) invented a 
>non-fuzed, high-explosive incendiary semi-armor piercing technology, that 
>they sell world wide.  They have published brochures on it.  The U.S. 

And which is being manufactured all over the world in various calibres.
The rounds in fact penetrate more than normal, cored AP-rounds do. The
deformable nose helps penetration at high angles and the explosion does
so, too. 

The history of these rounds is in tests, where the Norwegian army
noticed that practice rounds do more damage than fragmenting, explosive
rounds! So, they started to develop the idea further and add part of
the properties of both rounds. The result is pretty impressive, I've
fired the same bullets in 12,7 mm calibre and they really do a lot of
damage compared to a normal bullet.

The technology is just a long list of fine tuning. You need to have a
suitably sensitive explosive, hot enough inciendary mixture, the
support plate thickness and hole diameter matter a lot, the core
material is also pretty critical for the function. You want to have a
couple of milliseconds delay before the explosive goes off and to get
exactly that much is not going to be easy. However, once the parameters
are set, making the ammunition is really cheap compared to fuzed
shells.


ArNO
    2

Newsgroups: alt.engr.explosives
From: arno@utu.fi (Arno Hahma)
Subject: Re: 20mm. shell.
Organization: University of Turku
Date: Sat, 16 Sep 1995 18:03:41 GMT

In article <438bq3$15p6@usenetw1.news.prodigy.com>,
Arkon Kalashki <WHQA19A@prodigy.com> wrote:

>accellerating vehicle).  Further, the arming is delayed until the round 
>is not a danger to the weapon or its' crew.

This is normally done by using the rotation of the shell.
Additionally, all decent fuzes have a "primer safety". That is, the
primer is not in line with the firing pin until the round is at the
arming distance (usually varies from 30..500 m). Russian fuzes often
fail this property, that is, they have the primer and pin in line from
the beginning. That adds reliability, but decreases safety.

>Undoubtedly, malfunctioning arming/safety mechanisms contribute to the 
>approximately 15% dud rate.

15 % dud rate!?! I'd _never_ approve such a fuze to operational use.
The fuzes we use have far less than 1 % dud rate and most of the duds
are created by firing the shell into soft soil (swamp, for instance) in
a hard target mode. The AA artillery fuzes invariably have a
self-destruction device, that explodes practically all shells within a
safe distance (not back on ground).


ArNO
    2

From: knapper@bga.com (Woodrow W. Baker)
Newsgroups: alt.engr.explosives
Subject: Re: 20mm. shell.
Date: 19 Sep 1995 02:15:31 GMT
Organization: Real/Time Communications - Bob Gustwick and Associates

: Fascinating....the previous physical limitations of weapon caliber on use 
: of high explosive in the particular round seems now to have been 
: eliminated.  Of course, the practical considerations of using such a 
: small amount of explosive charge still would apply.  It seems now that it 
: would be practical to load HE in 12.7mm/.50 cal rounds.  

It has and is being done.  These rounds (SAPHIEE) come in 12.7mm (.50 cal)
20 mm , 25 mm, 30mm 60 mm and who knows what else.  The results are 
EXTREMELY impressive.  The actual loading pressures and incindiary 
compositions have been determined and they are reliable and reproducable.
There is a limited range of pressures that work.

Cheers
Woody



--
Woody Baker Postscript consultant/ hired software gun /flintknapper
knapper@bga.com        woody@knapper.cactus.org
"If you ain't bleedin' you ain't knappin'" -->go ahead, ask me!