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#1 TRYTRY

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Posted 15 June 2005 - 0744 AM

I read technical report arccb-tr-02013 safe maximum pressure determination for the M829E3/M256 cannon qualification program by David C. Smith & Eugene E. Coppola.
In the report, the Muzzle Velocity is little more than 5000ft/sec. I know the Muzzle Velocity of 125mm can reach 1700m/s(some round can reach 1800m/s). I can not believe M829E3 is so slow.
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Edited by TRYTRY, 15 June 2005 - 0814 AM.

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#2 Steeleagle

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Posted 15 June 2005 - 2003 PM

Remeber Speed of the Round doesn't always mean it's a good round.

The M830 series Tank rounds for the M256 gun flys at 1670 meters per second, but they found out that the Ballistics for the round when to crap at 1500 meters. So they scrap that series of rounds for the gun.

Edited by Steeleagle, 15 June 2005 - 2248 PM.

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#3 TRYTRY

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Posted 16 June 2005 - 0101 AM

Remeber Speed of the Round doesn't always mean it's a good round.

The M830 series Tank rounds for the M256 gun flys at 1670 meters per second, but they found out that the Ballistics for the round when to crap at 1500 meters.  So they scrap that series of rounds for the gun.

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Thanks, Steeleagle.
I have a question about your reply. My English is bad, I can not understand the "crap" you talk about. E=mv^2/2, high velocity is an advantage. I guess you mean the round in too high velocity will appear some problem, the velocity is almost 5Mach, it is the same problem with the aircraft flying in high Mach?
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#4 Wolfman

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Posted 16 June 2005 - 1505 PM

Thanks, Steeleagle.
I have a question about your reply. My English is bad, I can not understand the "crap" you talk about. E=mv^2/2, high velocity is an advantage. I guess you mean the round in too high velocity will appear some problem, the velocity is almost 5Mach, it is the same problem with the aircraft flying in high Mach?

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Note that I am generalizing below, there are newer designs on the Russian side that don't follow the pattern.


125mm APFSDS rounds generally have a higher muzzle velocity due to the fact that they are lighter than the 120mm counterparts. They are lighter because of a ) autoloader length constraints, and b ) the fact that they have a very small ring sabot, where the second point of support in the barrel is provided by the oversized fins (thus reducing the overall projectile weight).

However air resistance slows the penetrator down quickly due to those oversized fins.

So while the same round fired at a higher velocity WILL yield a higher kinetic energy, the rounds you mention (125mm sabots at up to 1700m/s and M829E3 at 1500m/s) are very different, muzzle velocity alone is not an accurate indication of overall performance. In fact M829E3 is supposed to be slower than M829A1 and A2 which it is meant to replace, even though it offers superior performance.

Edited by Wolfman, 16 June 2005 - 1505 PM.

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#5 Steeleagle

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Posted 16 June 2005 - 1626 PM

Note that I am generalizing below, there are newer designs on the Russian side that don't follow the pattern.
125mm APFSDS rounds generally have a higher muzzle velocity due to the fact that they are lighter than the 120mm counterparts. They are lighter because of a ) autoloader length constraints, and b ) the fact that they have a very small ring sabot, where the second point of support in the barrel is provided by the oversized fins (thus reducing the overall projectile weight).

However air resistance slows the penetrator down quickly due to those oversized fins.

So while the same round fired at a higher velocity WILL yield a higher kinetic energy, the rounds you mention (125mm sabots at up to 1700m/s and M829E3 at 1500m/s) are very different, muzzle velocity alone is not an accurate indication of overall performance. In fact M829E3 is supposed to be slower than M829A1 and A2 which it is meant to replace, even though it offers superior performance.

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thanks Wolfman on that.

What I mean by "crap" is that the round all the sudden in flight would start to wobble, or even tumble end over end in flight after 1500 meters because of the higher speeds. Understand that it is known that when a sabot dart is in flight, it will start to leighten itself in flight because of the High heat it is generating from the air it's flying through. The Higher the velocity of the Dart, the more unstable it is in flight to the target.

They could never figure why the Soviet 115mm Sabot round only had a max effective range of 1200, and the 125mm Sabot round has a max effective Range of 1600 meters. Until they made the the M830 Round and saw that the Higher velocity tends to make the rounds unstable in flight.
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#6 Wolfman

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Posted 16 June 2005 - 1707 PM

...the 125mm Sabot round has a max effective Range of 1600 meters.


I am not aware of a 1600m limitation for 125mm APFSDS ammo. Older models might not offer the penetration performance past that range, but they would certainly be able to hit the target.
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#7 Steeleagle

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Posted 16 June 2005 - 1726 PM

I am not aware of a 1600m limitation for 125mm APFSDS ammo. Older models might not offer the penetration performance past that range, but they would certainly be able to hit the target.

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Why do you think they when to Gun/missle systems with the AT-8 series fire out of a Raiper-3 125mm Gun, against targets over 2000m. Even after we stated it was " a Bad ideal" with the 152mm Gun/missle launcher system.

In US Army FM-90 series dealing with the Soviet Army, Soviet Tank doctrine calls for a full Tank platoon to Fire at one single Target. One of the reason is because the guns are not as capitable as gun systems in the west. One part of that is because of the Ammo fire by the Russian's gun systems. Their doctrine is base that three tanks has a better chance of hitting the Target then one. Grant you also the Factors of Sighting, Training, fire control add to it, but at lease 1/3 of the equation is the ammo.

We knew about these Limits since 1983 after Israel sent us several Captured T-72 in Lebanon that where intact but the Syrian Crews left them on the field, Motors running and the crews panic.

Edited by Steeleagle, 16 June 2005 - 1731 PM.

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#8 TRYTRY

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Posted 17 June 2005 - 0246 AM

Thanks.
I think USA's concept of tank round is just like USN's concept of BB round----heavier round is better than higher velocity. :)

Edited by TRYTRY, 17 June 2005 - 0247 AM.

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#9 Davout

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Posted 17 June 2005 - 1718 PM

Thanks.
I think USA's concept of tank round is just like USN's concept of BB round----heavier round is better than higher velocity. :)

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Well not really..

The E3 round may be slower and heavier for a couple of reasons.... All current armor technology is aimed at chopping a penetrator in pieces. The newest reactive armor works partially in that way. Certainly the new add on armor on the Leopard 2 acts that way. Angled moving metal plates will do nasty things to a long rod penetrator.

A good guess would be the heavier round is slower but potentially alot stronger. This would tend to prevent the breakup of the rod vs these armors.

Another factor may also be the DU itself. Several folks have claimed that the DU loses its capability of shearing off at higher velocities. This means that advanced ceramics would be more effective vs the round at higher speed. Essentially the DU would not be any better than tunsten. So, a heavy stronger and slower round may actually perform better even though its initial energy is lower.

All speculation of course...

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#10 TRYTRY

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Posted 17 June 2005 - 2220 PM

Well not really..

The E3 round may be slower and heavier for a couple of  reasons.... All current armor technology is aimed at chopping a penetrator in pieces.  The newest reactive armor works partially in that way.  Certainly the new add on armor on the Leopard 2 acts that way.  Angled moving metal plates will do nasty things to a long rod penetrator.

A good guess would be the heavier round is slower but potentially alot stronger.  This would tend to prevent the breakup of the rod vs these armors.

Another factor may also be the DU itself.  Several folks have claimed that the DU loses its capability of shearing off at higher velocities.  This means that advanced ceramics would be more effective vs the round at higher speed.  Essentially the DU would not be any better than tunsten.  So, a heavy stronger and slower round may actually perform better even though its initial energy is lower.

All speculation of course...

Davout

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Davout:
The add armor is just add the thickness of armor. One my friend tell me that APFSDS is hardly affect by the angle of armor, the add armor of the Leopard and chinese ZTZ-99 's Angle is the similar reason----the hatch of dirver.

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#11 Vasiliy Fofanov

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Posted 18 June 2005 - 2003 PM

I can not believe M829E3 is so slow.


Me neither. Considering that the power of the propellant has been increased considerably (hence all the efforts to recertify the gun tube to fire this round, new analysis for erosion peak points etc etc), I would expect the MV of the round to be higher than the current batch, at least in the 1700s of m/s.

It is possible that the velocity was deliberately reduced for the purpose of the modeling described in the article you are refering to, in order to account for far greater pressure persistence than would ever occur in real life. Prudent.

But to judge better I'll need to see the article itself. Any chance you may share?
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#12 Vasiliy Fofanov

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Posted 18 June 2005 - 2007 PM

The M830 series Tank rounds for the M256 gun flys at 1670 meters per second, but they found out that the Ballistics for the round when to crap at 1500 meters.  So they scrap that series of rounds for the gun.


Last time I checked, M830 line of rounds is one of the two types of rounds available to M1A1 since it's appearance, is there some other series of M830 rounds that popped up while I wasn't looking? And incidentally, M829A2 flies at 1680 m/s and does it just fine... You might want to get your facts straight ;)
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#13 Vasiliy Fofanov

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Posted 18 June 2005 - 2021 PM

Why do you think they when to Gun/missle systems with the AT-8 series fire out of a Raiper-3 125mm Gun, against targets over 2000m.


Really? I thought it was more like against targets at over 3000-3500m, but what would I know :rolleyes:

  Even after we stated it was " a Bad ideal" with the 152mm Gun/missle launcher system.

Well perhaps you just screwed it up? :)


In US Army FM-90 series dealing with the Soviet Army, Soviet Tank doctrine calls for a full Tank platoon to Fire at one single Target.


Pity Soviet tankers didn't study according to FM-90, I have trouble finding this recommendation in the Soviet version. Care to enlighten me how were Soviet platoons supposed to synchronise which tank to fire upon next? They had some hell of an IVIS apparently :D Incidentally in ODS there were multiple cases where Iraqi tanks were receiving several hits at once, I presume that's because M1A1 crews had doubts in their ability to hit and/or penetrate a T-55? :)

Their doctrine is base that  three  tanks has a better chance of hitting the Target then one.

Interesting. Not only they had a hell of an IVIS to agree which tank to target next, but their FCS apparently even benefited from each other's ballistic solution. "Gee, I wish we had one of them doomsday machines." :)

We knew about these Limits since 1983 after Israel sent us several Captured T-72 in Lebanon that where intact but the Syrian Crews left them on the field, Motors running and the crews panic.


Oh my, what a load of bull :rolleyes:
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#14 TRYTRY

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Posted 18 June 2005 - 2248 PM

Me neither. Considering that the power of the propellant has been increased considerably (hence all the efforts to recertify the gun tube to fire this round, new analysis for erosion peak points etc etc), I would expect the MV of the round to be higher than the current batch, at least in the 1700s of m/s.

It is possible that the velocity was deliberately reduced for the purpose of the modeling described in the article you are refering to, in order to account for far greater pressure persistence than would ever occur in real life. Prudent.

But to judge better I'll need to see the article itself. Any chance you may share?

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http://stinet.dtic.mil/
search M829E3
ADA406817 safe maximum pressure determination for the m829e3/m256 cannon qualification program
You can read they change the slug weight and charge weight, muzzle velocity is around 5100-5200 ft/sec.
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#15 Ssnake

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Posted 19 June 2005 - 0158 AM

What I am reading in this report is

Subsequently, the test procedure was altered to maintain charge temperatures and propellant weights and to vary the projectile weight to change the pressure.

...given that the goal of the test was to ascertain that the firing of the M829A3 was safe even under adverse conditions (e.g. high propellant temperatures, upper limit of manufacturing accuracy for propellant and projectile mass), it seems to me that the projectile mass was deliberately increased to test these conditions. Consequently, the muzzle velocity must be lower than that of the real M829A3. This test series simply is unsuitable to estimate the true v0 of it.
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#16 DKTanker

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Posted 19 June 2005 - 1112 AM

Last time I checked, M830 line of rounds is one of the two types of rounds available to M1A1 since it's appearance, is there some other series of M830 rounds that popped up while I wasn't looking? And incidentally, M829A2 flies at 1680 m/s and does it just fine... You might want to get your facts straight ;)

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You are correct, Vasiliy. The M830 is the 120mm service HEAT round with a MV in the vicinity of 1150 m/s. The M831 is the practice HEAT round. M827 (never fielded), M865 familiy, practice TPFSDS, and M829 series are the 120mm APFSDS rounds that the US military uses. I don't know from where steeleagle gets his facts, but I've fired multitudes of M830 and M831 with great accuracy. Same same with M829 and M829A1. By all accounts M829A2 was just as accurate during this last go around. Now it could be that steeleagle is refering to M833, 105mm APFSDS, which was notoriously inaccurate during initial testing. Accuracy problems finally resolved just as M1A1s were being fielded.
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#17 Vasiliy Fofanov

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Posted 19 June 2005 - 1237 PM

http://stinet.dtic.mil/
search M829E3


The site doesn't reply. I was probably deemed unworthy :mellow: Anyway, I'll probably support Ssnake's conclusions anyway, it's very likely not the actual MV of an actual round. With nearly 12 kilos of new high-energy propellant instead of the 8.7kg JA-2 in M829A2, I actually expect it will have the highest MV out there, even higher than early 125mm feather-light rounds.
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#18 Paul Lakowski

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Posted 19 June 2005 - 1335 PM

When you see a projectile with an "E" designation, its usually means experimental. One of the most important aspects is to explore parameters, so these figures may just be reflecting such a test. ...and therefore not reflective of the final production performance, which I thought was in the region of >1800m/s?. AS i recall the M-829A2 reached 5500ft per second muzzle velocity and A3 model reportedly exceeded that by around 10%.
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#19 DKTanker

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Posted 19 June 2005 - 1406 PM

When you see a projectile with an "E" designation, its usually means experimental.

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To add, if one goes to the link in one of the previous posts, and looks at the abstracts, it becomes readily apparent that many differing combinations of propellent weight, projectile weight, projectile configuration, propellent composition, and MV are being tested. To draw any definitive conclusions from 'E' testing, from only information that is in the public domain, is a fools errand. Much ado about nothing I'd say....not enough information.
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#20 Wolfman

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Posted 19 June 2005 - 1444 PM

Thanks for the clarification guys, I assumed the initial info was correct. Yeah yeah I know about ASSuming... :o
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