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Message 1 in thread
From: John D Wilkinson (jwilkins@wilde.oit.umass.edu)
Subject: AP Ammo info?
Newsgroups: sci.military.moderated
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Date: 1995/09/20
From jwilkins@wilde.oit.umass.edu (John D Wilkinson)

First, I would like to thank all those who replied to my earlier post and 
patiently explained the exact differences between HE, HEAT, and AP rounds 
for tank guns.

The distinct impression I got after reading all the replies was that U.S.
APFSDS-DU rounds were by far the most effective round for use against 
modern MBTs.

So, my question is, does anyone have any info regarding the mass, length, 
diameter, muzzle velocity, and RHA penetration of the U.S. 105mm 
and 120mm rounds of this type?

Are there any effective countermeasures being developed against this type 
of KE attack?  Most of what I have read seems to indicate that the only 
thing that can stop a KE attack of this type is mass of the armor.  Is it 
true that the only thing that matters is the cross-sectional density of 
the armnor presented to the penetrator?  If it is, then it seems that 
efforts to increase the strength to weight ratios of armor materials 
through use of advanced alloys or composites will all be in vain.

If find this a disturbing prospect, to say the least, because if it is 
true, then, short of escalating the weight of the MBT into the 100-ton 
class, there will be no way to protect one's MBTs against enemy tank fire.

If anyone can shed some light on this dillema, or reccommend a source of 
information, I would greatly appreciate it.

Thanks in advance.
--
John Wilkinson
jwilkins@oitunix.oit.umass.edu
Message 2 in thread
From: Stan C. Crist (stanc@pcsi.cirrus.com)
Subject: Re: AP Ammo info?
Newsgroups: sci.military.moderated
View this article only
Date: 1995/09/20
From stanc@pcsi.cirrus.com (Stan C. Crist)

John D Wilkinson (jwilkins@wilde.oit.umass.edu) wrote:

: So, my question is, does anyone have any info regarding the mass, length, 
: diameter, muzzle velocity, and RHA penetration of the U.S. 105mm 
: and 120mm rounds of this type?

For 120mm M829A1 (APFSDS-DU) ammo:

Total weight:         45.7 lbs
Projectile weight:    18.0 lbs
Propellant weight:    20.0 lbs
(Remaining weight divided between the combustible case,
 case head, aluminum sabot)

Projectile length:    30.7 inches
(No, that's not a typo.)

Muzzle velocity:      5160 fps

Stan
Message 3 in thread
From: Colin Campbell (colinc@ix.netcom.com)
Subject: Re: AP Ammo info?
Newsgroups: sci.military.moderated
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Date: 1995/09/22
From colinc@ix.netcom.com (Colin Campbell)

In <DF6Hw3.GGJ@ranger.daytonoh.attgis.com> jwilkins@wilde.oit.umass.edu
(John D Wilkinson) writes: 

>So, my question is, does anyone have any info regarding the mass, length, 
>diameter, muzzle velocity, and RHA penetration of the U.S. 105mm 
>and 120mm rounds of this type?


            Muzzle Velocity (m/s)        Mass

 120mm
   M829             1670                    9.41 lb
   M827             1650                    9.98 lb
   DM13 (German)    1650                    9.78 lb
 105mm
   M833             1493.52                 8.6  lb

Please note that the M829A1 (120mm) and the M900 (105mm) figures are
absent.  As these two rounds are the "latest and greatest" thier
performance data has not been released.

 Assume that the approximate projectile diameter is about 40mm.

>
>Are there any effective countermeasures being developed against this type 
>of KE attack?  Most of what I have read seems to indicate that the only 
>thing that can stop a KE attack of this type is mass of the armor.  Is it 
>true that the only thing that matters is the cross-sectional density of 
>the armnor presented to the penetrator?  If it is, then it seems that 
>efforts to increase the strength to weight ratios of armor materials 
>through use of advanced alloys or composites will all be in vain.

  There are several types under laboratory development right now.  One
type uses moving plates to snap the projectile, and another uses armor
that "gives" enough to cause the projectile to turn sideways rather
than bore straight in.  Both of these exist only in computer models
(allthough the Russians are rumored to have a laboratory sample of
"snapper" armor) _if_ these can be incorporated into actual tanks is
the question.
Message 4 in thread
From: Darrel Dearing (ddearing@myriad.com)
Subject: Re: AP Ammo info?
Newsgroups: sci.military.moderated
View this article only
Date: 1995/09/22
From ddearing@myriad.com (Darrel Dearing)

In article <DF6Hw3.GGJ@ranger.daytonoh.attgis.com>, 
jwilkins@wilde.oit.umass.edu says...
>
>Are there any effective countermeasures being developed against this  type 
>of KE attack?  Most of what I have read seems to indicate that the only 
>...

  The cheapest and easiest way to defeat an AP projectile is to put more 
mass between you and it (thicker or higher-density armor).  Modern 
composite armor is more resistant to penetration than simple steel plate, 
but not to the same level that it defeats HEAT rounds.
  I have seen occasional claims that reactive and active armor can defeat 
and APDS-type round by knocking it off-axis, causing it to hit at an 
angle, but not anything more conclusive than manufacturer's claims.

ddearing@mail.myriad.net
Message 5 in thread
From: George Swan (gswan@io.org)
Subject: Re: AP Ammo info?
Newsgroups: sci.military.moderated
View this article only
Date: 1995/09/25
From gswan@io.org (George Swan)

In article <DFBKr7.G9K@ranger.daytonoh.attgis.com>,
Darrel Dearing <ddearing@myriad.com> wrote:
>
>From ddearing@myriad.com (Darrel Dearing)
>
>In article <DF6Hw3.GGJ@ranger.daytonoh.attgis.com>, 
>jwilkins@wilde.oit.umass.edu says...
>>
>>Are there any effective countermeasures being developed against this  type 
>>of KE attack?  Most of what I have read seems to indicate that the only 
>>...
>
>  The cheapest and easiest way to defeat an AP projectile is to put more 
>mass between you and it (thicker or higher-density armor).  Modern 
>composite armor is more resistant to penetration than simple steel plate, 
>but not to the same level that it defeats HEAT rounds.
>  I have seen occasional claims that reactive and active armor can defeat 
>and APDS-type round by knocking it off-axis, causing it to hit at an 
>angle, but not anything more conclusive than manufacturer's claims.

This is something I have wondered about for a long time.  Why should
armour plate be dense?  Why should it be a plate at all?

As I understand it, smaller, higher velocity, projectiles are more
powerful because they surrender their energy more quickly.  So what
if you used the same mass of armour, but you stretched it, leaving
lots of tiny empty spaces, so that your kinetic energy projectile
had more time and distance to decelerate?  You could make the outer
layers really springy giving the long rod penetrators more opportunity
to twist and spread their punch over a larger area.

Further, you could put those outer layers under stress, just like
the inner layer of a high velocity cannon.  I don't know how you
would do this with a plate, but what if you took a plate, cut those
offset parallel slits they put in expanded metal (ascii diagram
follows), and then twisted them into coils, cones or helices?
Anyhow, if you leave the idea of it being a plate behind, you should
be able to store some potential energy in it.

plate with slits	expanded plate
||||||||||||||||||||	 // \\ // \\ // \\ // \\ // \\ // \\ // \\ // \\ / <<   >X<   >X<   >X<   >X<   >X<   >X<   >X<   >X<
||||||||||||||||||||	 \\ // \\ // \\ // \\ // \\ // \\ // \\ // \\ // \ X< 	>X<   >X<   >X<   >X<   >X<   >X<   >X<   >
||||||||||||||||||||	 // \\ // \\ // \\ // \\ // \\ // \\ // \\ // \\ /

Read the rest of this message... (25 more lines)

Message 6 in thread
From: Darrel Dearing (ddearing@myriad.com)
Subject: Re: AP Ammo info?
Newsgroups: sci.military.moderated
View this article only
Date: 1995/09/27
From ddearing@myriad.com (Darrel Dearing)

>This is something I have wondered about for a long time.  Why should
>armour plate be dense?  Why should it be a plate at all?
>
  The reason current armor is composed of dense armor plates is that it 
is the tensile strength of the armor which causes the projectile to slow 
down.  Spaced armor as you have described is effective against HEAT and 
HESH/HEP rounds, as the effects of those rounds do dissipate over 
distance on their own.  
  The resitance of armor to kinetic rounds, for a given material, 
increases roughly with the thickness of the armor squared.  This is the 
reason the main armor is generally a single slab, with an incline of 60 
degrees or more.  A modern tank will have a frontal armor thickness 
equivalent to over a foot of steel (some sources indicate 18 inches on 
the latest Western designs).  If that were broken into even two equal, 
spaced segments, your effective protection would be 50%-100% of the 
effectiveness of the single plate (guesstimate).  This is why spaced 
armor generally consists of thin outer shells (maybe capable of stopping 
small arms and fragments) followed by a space (increasingly filled with 
fuel or inert materials to increase dissipation of HEAT rounds) followed 
by the big plate.
  Please note, this is not dogma, just my (unclassified) informed 
opinion.	

ddearing@mail.myriad.net
Message 7 in thread
From: Stan C. Crist (stanc@pcsi.cirrus.com)
Subject: Re: AP Ammo info?
Newsgroups: sci.military.moderated
View this article only
Date: 1995/09/25
From stanc@pcsi.cirrus.com (Stan C. Crist)

John D Wilkinson (jwilkins@wilde.oit.umass.edu) wrote:

: ...does anyone have any info regarding the...U.S. 105mm (ammo)?

For 105mm M900 (APFSDS-DU) ammo:

Total weight:         41.0 lbs
Projectile weight:    15.1 lbs
Propellant weight:    13.5 lbs
Projectile length:    28.0 inches

Muzzle velocity:      4938 fps

Stan

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