Military History | How To Make War | Wars Around the World Rules of Use How to Behave on an Internet Forum
Armor Discussion Board
   Return to Topic Page
Subject: Revolution in American Tank Gun and Ammunition
dwightlooi    10/13/2007 6:20:10 PM
The revolution in American Tank Gun and Ammunition

For much of the 1970s and 1980s, American tank gun ammunition development has been pretty much a mirror of similar developments by European allies. In fact, the US adopted first a British gun (L7A1) then a German gun (M256), firing similar APFSDS ammunition as those used by European armies except for the US preference (partly due to material availability) for Depleted Uranium penetrators while European armies preferred Tungsten alloys. However, this changed in the last decade as philosophies between American and European developers diverged in response to the latest threats.


American tank gun philosophy

The current direction of American tank gun and ammunition development differs from European practices in three different ways. First, America now favors a SLOWER, heavier long rod penetrator over one with the highest muzzle energy and velocity. Second, America has no intent or desire to adopt longer, heavier barreled weapons similar to the Rheinmetall 120mm/L55 or the Giat 120mm/L52, in fact the next generation gun being developed is an L43 weapon that is one caliber shorter in barrel length and lighter than the current 120mm/L44 on the Abrams MBT. Lastly, America has developed a taste for 12km range tank gun ammunition for use with third party designation or autonomous homing guidance.


The Slower, Heavier Rod

The latest sabot round fielded by the US Army is the M829A3. This round fires a long rod that is the longest possible for the legacy 120mm cartridge dimensions with the rod spanning the maximum allowed cartridge length right down to the front of a newly shortened ignitor cap. The 7kg, 924mm long, penetrator is longer, larger in diameter and heavier than that used in say the contemporary German DM63 ammunition (5kg, 745mm long). This long rod round however has a rather low muzzle velocity amongst modern Sabot rounds -- at 1550 m/s it is about 200m/s slower than the German DM63 for instance. But, the 10kg the projectile one heavy slug with the penetrator itself being much thicker in diameter in addition to being longer and heavier than european designs. Its manufacturer, ATK, believes that the round offers similar penetration performance shot out of a 44-caliber barrel as the latest German ammunition shot out of a 55-caliber tube. In addition, the design is believed to be much more resilient to the shearing action of "heavy" reactive armor and is designed to penetrate all existing Konkat style armor with negligible or no degration to penetration performance.

M829A3 - Depleted Uranium APFSDS-T round
http://img151.imageshack.us/img151/1598/m829a3ke8.jpg">

DM63 - Tungsten APFSDS-T round
http://img151.imageshack.us/img151/751/dm63ne0.jpg">


The Shorter, Lighter Gun

Almost in direct contradiction to the European tank gun trend towards longer, heavier 52~55 caliber weapons such as the Giat 120mm/L52 on the Leclerc and the Rheinmetall 120/L55 on the Leopard 2A6, the latest US gun being developed is lighter and a tad shorter than the 120mm/L44 M256 weapon on the Abrams MBT. The XM360 will be roughly 43 calibers long and weigh a paltry 4100 lbs for the entire gun system. This puts it at less than half the weight of the Rheinmetall 120/L55 mounting (9100 lbs). This is partly driven by the desire to make a 120mm weapon available to light FCS vehicles being developed (20~35 tons) and partly due to the believe that the next major step up in tank gun lethality cannot be had with longer and heavier guns anyway. For instance, the Rheinmetall 120/L55 fires the DM63 ammunition with 7% more velocity and 15% greater impact energy than the same round fired from a Rheinmetall 120/L44. While this is no doubt a tangible improvement it neither dramatically improves lethality nor offer a tangible increase in effective engagement range. The next major leap in tank gun lethality will have to come from somewhere else.

http://img401.imageshack.us/img401/6659/xm360m256cg5.jpg">
http://img401.imageshack.us/img401/3325/xm360ja0.jpg">
http://img401.imageshack.us/img401/9245/xm360firingrz6.jpg">


The Guided Medium Range Munition (MRM)

The US is currently developing two guided, rocket assisted anti-tank rounds with a range of 12 km. In some ways these are similar to gun launched missiles such as the MGM-51 and those used by Russian tanks. The big difference is that unlike other ATGMs, these are launched at full
 
Quote    Reply

Show Only Poster Name and Title     Newest to Oldest
Pages: PREV  1 2 3 4 5 6 7 8 9 10   NEXT
dwightlooi       10/17/2007 8:14:30 PM

Let me put it very simply for you...

A 5~15mm steel plate blast apart by a high explosive charge at 0 degrees to a long rod does not erode it in any meaningful way. The effect is similar to the rod striking a 15mm steel plate added to the hull ? which is practically nothing. A heavy ERA plate blown up at an angle of 40~70 degrees has some a MINIMAL eroding effect on the long rod too. The critical effect is not the minimal erosion which is very similar to a long rod impacting a thin steel plate at a shallow angle. The critical effect is that when the long rod contacts the retreating (or stationary) rear plate while still in contact with the front plate, a hearing load is applied to the rod which sometimes causes the rod to break where it contacts the REAR plate. But it frequently doesn?t break either. A LOT of whether it breaks or not is determined by the robustness of the rod and by the position on the ERA brick the penetrator strikes.

It is not sufficient that a penetrator strikes the ?heavy? era brick. To break a rod it is necessary for:-

(1)     The rod to be relatively fragile or willowy.

(2)     That the rod strikes near the middle of the brick ? otherwise the rod will not have contacted BOTH the front and the rear plates for a long enough duration (if at all) for maximum shearing to occur and it really takes most if not all of the shearing potential to break a rod.

(3)     That the rod strikes at the right angle ? too steep and it?ll be almost like a straight on impact with zero shearing effect, too shallow and the rod again the contact time on both front and rear plates become minimal.

The combination of conditions required is such that the ERA is rather unreliable at stopping long rod penetrators. ERA doesn?t cover all of the frontal arc and only around center 20~40% of EACH brick is capable of applying sufficient shear whereas the rest of the brick is ineffective. And these 20~40% of each brick only works against the weaker long rods and not all. Even when the rods do fracture, they still penetrate to about 60~80% of their original ability may still defeat the rather pathetic cast base armor of Russian tanks.

The reason western ammunition designers improve long rods is simply to ensure that the long rod will penetrate ALL the time, every time, within effective range not 70% of the time or 80% of the time. In this respect, an Abrams for example is much better protected than a T90 with the latest ?heavy? ERA package ? the DU faces laminate armor simply stops the long rods.

 
Quote    Reply

earlm    Your scenario is unrealistic   10/17/2007 10:33:08 PM

I wanted to say that I am not making any free advert for SB ;-)

Herald asked so I answered .

*************************

I 'm not defending ERA without reasons . In the West , we have a much
better armor design than in the East because of our better knowledge
about alloys and better manufacturing of expensive and high quality
materials . We also have a better technology regarding Tank rounds .

But ERA is a cheap and light way to turn a medium Tank into a well armored still
medium Tank . Russia is so far the only one to field decent ERA . All
the others ~France , Israel , the UK and some other Eastern Nations
(China comes to mind) are only fielding NERA or weak ERA .

ERA is not the panacea , far from it , but it works well when you know
how to build it . The latest Russian stuff can be a nightmare for a
Tank Gunner and a tiring task for the loader , lol ! (It 's why the
Leclerc has an autoloader . {Just kidding}) .



Let 's put that into perspective .

Let 's say that an Abrams SEP with M829A2 is facing a T-80UM1 with 3BM42 @ 4000m .

The T-80 will fire first a Reflex or two at the Abrams (you can unload
a round from the breach in a T-80 and switch to a Reflex missile while
you can 't unload a round on an Abrams . When it 's in , it has to be
fired)

The Reflex might hit or miss . If it hits , expect to get some problems
with your optics and/or with your FCS (your TIS can also go Out Of
Order) . That 's a bad start .

If it misses , the Abrams TC will keep his Tank at almost full speed to
close in ASAP to get in range (He wants to fire too and ASAP !) .

Now the two Tanks are about 3000m from each other , both will start to
use their APFSDS . The rate of fire is on the T-80 side because loading
a round when the Tank is at full speed in the countryside ~as I 've
been told many times by US , English and German loaders~ is not an easy
task . An autoloader doesn 't care .

Now , all comes to the gunners and especialy the Abrams 's gunner . If
he can aim low and target the glacis or the lower hull , the T-80 will
die . If he hits the front or the side turret , this is a 50/50 chance to fail to penetrate .

During that time , the T-80 did fire too . The Du rod will hit the
Abrams somewhere ... If it hits the front or side turret , the Abrams
will survive but if it hits the lower hull or the glacis , we have one
Abrams down .

You can see that it is a very undecided fight when plotted against each other alone .

 

I have to say that it would probably be the same if your replace the Abrams with a Leo2A5 or a Leclerc or a Chally .

I may say that the Leclerc and the Chally have a better chance because
they both can fire at a longer range than the Abrams which has a 4000m
maximum range (FCS restriction , the LRF {Laser Range Finder}is the
culprit) .

*********************

It is very easy for us to say that the Russian made Tanks are not good . Well , that 's untrue .

Fortunatly , some people are more clever than some poster here and try to think how to deal with Reflex and ERA ...

(about Reflex missiles , we still do not have a proper defense against them while the Russian have ARENA to stop our ATGMs) .



Cheers .


This scenario resembles a medieval joust more than any real armor tactics I know of.  Yes, it is possible two tank forces would blunder into each other but it is not likely.  Especially an American force with the US level of surveillance.  Most armor simulations I know of (RAND) posit an attacker and a defender.  I don't see the T-80 succeeding as an attacker.  As a defender, I think Refleks helps a lot.  But when would a US commander send unsupported M-1s against dug in T-80's?  Never.  At the least they would have smoke and most likely air support.  The tank is part of a system and I think it is clear that Western armor helps its tanks be part of that system more effectively than ERA helps Russian tanks.  What happens after the initial engagement, do they get new ERA?  How long does it take to mount?



 
Quote    Reply

Jeff_F_F       10/18/2007 9:09:43 AM
Looking at the side view, it looks like it should swap out pretty simply. I'm not sure how how heavy it is but I'd suspect that it can probably be manhandled into place by the crew.
 
On the other hand, looking at that side view again, I'm struck by the amount of the vertical region of the side of the turret is unprotected against a horizontal shot. It looks like about 50% chance that any shot is going to completely miss either the back plate or the front plate, or in the case of the lower 15% or so, both.
 
Quote    Reply

Bluewings12       10/19/2007 12:01:48 PM
Herald :
""The LRF, whatever tank it is mounted in, is LOS reflection limited, so you don't know what you write.""

Don 't be silly Herald , it 's you who do not know what you speak about . Of course it is LOS limited but in flat terrain (ie : desert , etc ...) a Chally or a Leclerc can fire at over 5000m if needed when the Abrams is limited to 4km because of its LRF maximum range . If an Abrams 's gunner wants to fire at over 4000m , he can 't rely on his LRF and have to guess the range (not an easy task) then input the range manualy (Abrams SEP and not M1A1-HA) , then work out the elevation of the gun manualy again .

""
Stick to the armor and leave the  EW to others.""

Speak to the Hand . I know my stuff .

Dwightlooi :
""
A 5~15mm steel plate blast apart by a high explosive charge at 0 degrees to a long rod does not erode it in any meaningful way. The effect is similar to the rod striking a 15mm steel plate added to the hull which is practically nothing.""


Wrong . A steel plate added to the hull ~or the turret~ is static while an extremly fast moving plate has its own energy . As an exemple , drive your car at 40mph and hit face on a stopped car , then try again and hit a another car moving towards you ...
The result will be very different !  What you said is simply stupid , don 't you think ?

""
A heavy ERA plate blown up at an angle of 40~70 degrees has some a MINIMAL eroding effect on the long rod too.""


Minimal ?!  Well , it can erode the rod by as much as 10% (up to 7cm for a 70cm rod) as I said before . Then , there is also the retreating plate who can erode the rod by as much as 15% (up to 10cm for a 70cm rod)  .
In the worse can scenario , the rod sandwitched between the 2 plates will yaw and simply break .

""
The critical effect is that when the long rod contacts the retreating (or stationary) rear plate while still in contact with the front plate, a hearing load is applied to the rod which sometimes causes the rod to break where it contacts the REAR plate.""

Exactly .

""
the ERA is rather unreliable at stopping long rod penetrators""

Not really , in fact it does a rather good job . Of course it depends of the penetrator itsel , an M829A3 have a big chance to defeat Kontakt-5 or Kaktus , but the "Silver bullet" M829A1 will struggle ...

Earlm , my scenario is not unrealistic . Whatever Air Support you have , 2 Tanks can face each other anytime .
I used such a scenario to demonstrate a possible outcome and not to talk about the strengh of the US Forces and the weakness (?) of a potential enemy .

Cheers .

 
Quote    Reply

Herald1234       10/19/2007 12:14:58 PM
I warned you, BW.

Eyesafe laser rangefinder.

Refer to page two.

Type
Laser type
Wavelength
Maximum pulse energy
Typically applied pulse energy
Maximum repetition rate
Beam divergence (1/e2)
Laser class
Eye-safe distance (NOHD ?
NominalOcular Hazard Distance)
Receiver
Detector type
Field of view
Range data
Measuring accuracy
Measuring range
Multiple target resolution
Multiple target indication
Logic
Nd: YAG, Raman shifted
1543 nm ± 5 nm
14 mJ
approx. 10 mJ
1 Hz
0.5 mrad
1 in accordance with ANSI
Z136.1-2000
0 m
InGaAs-APD
approx. 0.8 mrad
± 5 m
200 to 9,995 m
&S804; 20 m
Yes
First / last echo
Abrams M1
Determine the range ? take action
The eyesafe laser rangefinder (ELRF) on the M1 Abrams main
battle tank is used to determine the distance to recognized
and acquired targets on the battlefield. The ELRF can determine
ranges from 200 m to 9995 m depending on weather condi -
tions and the target itself.
In the M1, the ELRF is integrated into the gunner?s primary
sight (GPS). A visible, collimated reticule is projected into the
GPS, providing the aiming device for the main and secondary
weapon of the M1. Control and data output of the laser rangefinder
is possible either via the defined parallel interface for
the sight on the M1 tank or via an RS 422 serial interface.
The ELRF generates the laser radiation using a tested, qualified
Raman-shifted Nd: YAG laser that is not harmful to the eye.
This technology provides outstanding performance data for a
laser rangefinder.
crosshairs
Wavelength
Mechanical interface
Dimensions (W x H x L)
Weight
Electrical interface
Power supply, ELRF
crosshairs
Power consumption
Interface
Ambient conditions
Operating temperature
Storage temperature
660 nm ± 15 nm
approx. 108 x 295 x 223 mm3
Approx. 11 kg
18 ? 30 VDC
24 ± 6 VDC
Peak &S804; 150VA
Standby &S804; 50VA
Parallel interface for operation,
range data and bite
RS 422 serial interface
? 32°C to + 63°C
? 51°C to + 72°C
Technical data
Carl Zeiss Optronics GmbH
Carl Zeiss Gruppe
73446 Oberkochen
Germany
Tel.: + 49 73 64 20-65 30
Fax: + 49 73 64 20-36 97
optronics@zeiss.de> /optronics

Now step off, poseur2.

Herald



 
Quote    Reply

Bluewings12       10/19/2007 12:51:37 PM
Herald , I might not have made myself very clear . I am sorry Gentlemen .
I was supposed to say that it was the FCS the culprit because it can only propose firing solutions up to 4000m .
(Ooops)

Cheers .

 
Quote    Reply

Herald1234       10/19/2007 1:00:49 PM

Herald , I might not have made myself very clear . I am sorry Gentlemen .

I was supposed to say that it was the FCS the culprit because it can only propose firing solutions up to 4000m .

(Ooops)



Cheers .


If the Challenger can hit targets at 5000 meters then so can the Abrams.

CREF the SAME Canadian fire control system that BOTH tanks use.

That will be OOPs twice.

Herald
 
Quote    Reply

dwightlooi       10/19/2007 7:57:06 PM

Herald,

Most of the above posts are UTTER RUBBISH.

(1) The Abrams has no Laser Range Finder limitations at all -- I don't know where that myth came from. It can shoot range up to the ballistic range of ANY current ammunition. Basically, anything that currently leaves the Rheinmetall 120/L44 cannon will hit the ground at a range below the maximum range of the LRF.

(2) The Abrams has no FCS limitations out to ANY range. Again I don't know where this nonsense is coming from.

(3) The limitations on APFSDS range is due to the decreasing performance of KE penetrators with range as they slow down. Approximately 5~6 MJ is required to penetrate the frontal armor of contemporary MBTs. This corresponds to a residual velocity of 900~1000m/s, any slower and the long longs become ineffective.

(4) The limitations on HEAT range is due to the slow flight speed and dispersion of HEAT projectile. At longer ranges (somewhere beyond 5 km) they are simply not accurate enough (due to their own dispersion or unpredicted target movement during flight time) that they'll miss more than 75% of the time.
 
Quote    Reply

Herald1234       10/19/2007 8:13:06 PM


Herald,

Most of the above posts are UTTER RUBBISH.

(1) The Abrams has no Laser Range Finder limitations at all -- I don't know where that myth came from. It can shoot range up to the ballistic range of ANY current ammunition. Basically, anything that currently leaves the Rheinmetall 120/L44 cannon will hit the ground at a range below the maximum range of the LRF.

(2) The Abrams has no FCS limitations out to ANY range. Again I don't know where this nonsense is coming from.

(3) The limitations on APFSDS range is due to the decreasing performance of KE penetrators with range as they slow down. Approximately 5~6 MJ is required to penetrate the frontal armor of contemporary MBTs. This corresponds to a residual velocity of 900~1000m/s, any slower and the long longs become ineffective.

(4) The limitations on HEAT range is due to the slow flight speed and dispersion of HEAT projectile. At longer ranges (somewhere beyond 5 km) they are simply not accurate enough (due to their own dispersion or unpredicted target movement during flight time) that they'll miss more than 75% of the time.
I wonder if I'm part of the trash?

No seriously, most of what you described I knew already [ballistics is part of my toolkit] just by public information and a little applied mathematics, but I tend to laser focus on the obvious glaring errors. I am NOT an expert on armor; but I can work out most of the BS I see using what I know.

Herald
 

 
Quote    Reply

Bluewings12       10/20/2007 6:51:51 PM
Sorry , I could not answer sooner , I 'm having a busy week-end .

Dwightlooi :
""(2) The Abrams has no FCS limitations out to ANY range. Again I don't know where this nonsense is coming from.""

Yes it has . Ask any Abrams gunner , he 'll tell you that when you lase something at over 4000m , you don 't get any range and the digital readings in gunner sight show four dashes "- - - -" instead of a range . Believe me , I know  . I 've always been one of the best gunner at eSim and some Abrams and Bradley gunners from FT Knox can back me up ;-)

Herald :
""
If the Challenger can hit targets at 5000 meters then so can the Abrams.
CREF the SAME Canadian fire control system that BOTH tanks use.""

Nope .
"The Challenger 2's fire control system is the latest-generation digital computer from Computing Devices Company (CDC) of Canada and is an improved version of that installed in the US M1A1 Abrams tank."
The British don 't give much details about it but what I know is that the system can compute a firing solution well over 4km  , I saw a picture taken from the sight .

Cheers .


 
Quote    Reply
PREV  1 2 3 4 5 6 7 8 9 10   NEXT



 Latest
 News
 
 Most
 Read
 
 Most
 Commented
 Hot
 Topics