Tank Guns and Ammunition

[collegeboy16]

Why does the Rheinmetall 120mm gun have a larger bore evacuator than say its eastern 125mm counterparts?

 

[militarysta]

Optimum velocity For all now avaible APFSDS it's less then 1750m/s.

 

[militarysta]

Very interesting part about Soviet APFSDS munition posted on otvaga by one user:

those vlues are very very close to other sources, propably they are taken form manuals.

And other data from otvaga -as countrargument that "bigger" gun (bigger caliber) means more propelant charge:
15-мм 3БМ28 - масса пороха 8100 г.
125-мм 3БМ42 - масса пороха 8200 г, то есть примерно такая же.
А в 120-мм DM53 например - 8400 г.

 

[asianobserve]

Some historical tidbits: WW2 era T32 rifled 120mm tank gun based on the M1 Anti-Aircraft Gun (dubbed as "Stratoshpere Gun" since it was the first operational gun that can reach the stratosphere)

T32

M1 AA Gun

 

[militarysta]

CL-20 is 60 times more powerful than RDX.

AFAIK 120 mm HEAT with RDX penetrates around ~250-300 mm. If replaced with CL-20 tandem warhead and Obus-G type ball bearings, penetration could be around ~1200 mm or more. Only thing, mass production will be very costly unless orders of more than 30000 or 40000 are placed. I suppose that one round would require around 3 kg of CL-20. 'Adequate quantity' should be around 2 tonnes. so we can make 670+ warheads now already.

If MoD approves the fielding of this round,

R.I.P - Pakistan tanks.

No it's not imposible. HEAT (SC) warhed is limited no by explosive but used (diameter) SC. For late 1990s it was 6-6,5x diamater so 120mm x6-6.5 = 720-780mm RHA in best case. And that value (800mm RHA) max is given for most modern NATO 120mm HEAT rounsd, and it's israeli analoge.
So there is no way to achive 900mm not even mentioned more mm RHA penetration.
They are avaible dozen of good pdfs about SC and HEAT warhed iinternet - mostly from balistic symposium- read them, it will explain you a lot.

 

[methos]

http://www.dtic.mil/ndia/2011ballistics/11770.pdf

There is no "60 more powerful than RDX" because there the power of explosive is not determined by a single factor. Going by TNT equivalency, HMX is between 10% better than RDX to 60% worse than RDX. RDX is also not used as explosive in shaped charges, but a mixture made up of different types of explosives (like for example "Compostion B"). Increasing just the amount or power of the explosives will also not lead to much, because the performance of shaped charges is depending on many factors - there won't be a linear increase in performance; once the optimum velocity is passed the increase in penetration will be very small, it could even come to a decrease in penetration performance.

 

[Kunal Biswas]

CL-20 or Octa-Nitro-Cubane is a Nitramine class of explosive 15 times more powerful then HMX or High Melting Explosive or Octogen, Given this the penetration value will increase dramatically compare to RDX / HMX types..

There are no HEAT round in the world use CL-20 but HMX or RDX variants, Only in India it will be used for Arjun Tank 120mm Rifled Cannon..

 

[The Last Stand]

Thanks Militarysta. But read my last post on the MBT thread. The penetration should be sufficient for what Indian Army is going to face. After all, we are not preparing to take on the Bundeswehr. :drunk:

Regards,
Keshav

 

[militarysta]

Given this the penetration value will increase dramatically compare to RDX / HMX types..

No, it will not.
I read all avaible in google pdfs about SC, HEAT, cumulative jest and others -including few PHDs works, and there is no option to "increase dramatically".
The best avaible now big caliber SC warhed have circa 8-9x diameter perforation.

 

[Kunal Biswas]

There is no data over internet about HEAT round using specifically CL-20 explosive to enhance penetration value, There are no research done based on that specific explosive, hence one cannot conclude conclusion..

No, it will not. I read all avaible in google pdfs about SC, HEAT, cumulative jest and others -including few PHDs works, and there is no option to "increase dramatically".The best avaible now big caliber SC warhed have circa 8-9x diameter perforation.

 

[methos]

Penetrations made by 30 g HMX shaped charge (right) and 30 g CL-20 shaped charge (left). Penetration performance increased by 40%, not by 15 times nor by 60 times. So a 120 mm shaped charge with CL 20 will penetrate less than 900 mm RHA.
This penetration is strongly dependant on standoff: During tests with Compostion A5 (which is up to 99% RDX) penetration increased by only 2% for a in-built standoff of 1 CD.
- Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI

 

[militarysta]

@UP
Kunal, explosive inside SC WARHED is only one, and definetly the not most iportant fractor.Using more powerfull explosive is blind way (wrong way). Jet velocity can't be faster then some value, what is more iportant -there is no sucht big difrences between penetration depth for jet whit velocity circ 6km/s and 12km/s - faster jet was developed on west to slighty overpas older ERA (Kontakt-1) without using precursor. The answer was using double working ERA whit extended reaction time between first and second layer. Now most of work on SC HEAT warhed are turning into mixed SC and EFP warhed what will give mucht better result then using only SC or EFP warhed. Here is no mirracle and no "wunderwaffe".
BTW: used explosive can't be to fast due to some time necessery to form "jet" in SC warhed

 

[militarysta]

Penetration performance increased by 40%, not by 15 times nor by 60 times.

Maybe im stupid but I can see there only 29%...

So a 120 mm shaped charge with CL 20 will penetrate less than 900 mm RHA.

Israeli clon of DM-12 whit completly new warhed have achivable 800mm RHA. And this round is now most fresh (on west) tank HEAT -developed for Merakava Mk.III/IV.

This penetration is strongly dependant on standoff: During tests with Compostion A5 (which is up to 99% RDX) penetration increased by only 2% for a in-built standoff of 1 CD.

2% sounds to be possible in known now aspects

 

[Kunal Biswas]

Thanks for sharing, very interesting information..

Though i will wait for our own results..

 

[methos]

Maybe im stupid but I can see there only 29%...

All RHA plates used in the tests have the same thickness. The shaped charge with CL 20 penetrated 7 plates, the warhead with HMX only 5. 7/4 = 1.4

 

[militarysta]

All RHA plates used in the tests have the same thickness. The shaped charge with CL 20 penetrated 7 plates, the warhead with HMX only 5. 7/4 = 1.4

Rather not in that way:
7-100%
5-x

x = 5*100/7
x=~71%

100% - 71% = 29%

So more or less 1.29 in best case?

 

[methos]

No. If I say "It penetrates x more than a HMX shaped charge", then the HMX shaped charge is being used as reference, hence 5 equals 100%. x = 7 plates are then 140%.
You are saying "The HMX charge penetrates only x percent of the CL 20's penetration".

 

[militarysta]

Oh, in that way You have right

 

[pmaitra]

Re: Tank Guns: Photo & Dicussion thread..

@Damian, M1A3 will have 120mm rifled gun. So much for your self styled outstanding knowldge of tank guns. remember how we debated it a few months ago?
Do you also remember my quote that Arjun Mk-3 will be a turretless tank with three men crew and much better protected than even Mk-2.

And where did you read that it will have rifled gun, and what rifled gun?

The only 120mm tank guns currently developed in USA, are smoothbore XM360 for lightweight platforms and XM360E1 for heavyweight platforms like MBT's.

http://www.dtic.mil/ndia/2010armament/WednesdayReunionDavidSmith.pdf
PDF from USA archieves DTIC, PDF original source is RDECOM ---> RDECOM | The United States Army

I did look up a bit, but I do not see any conclusive evidence that M1A3 will have rifled gun. @Decklander, could you please provide some references, like @Damian has?

This is all I found:

Main Gun improvements. Many years ago Jane's Defence Yearbook compared the Rheinmental smooth bore and Royal Ordinance rifled 120mm guns. It concluded that the rifled gun was the better weapon since it was more versatile. American and German operational experience has confirmed this.

Old news, from source: THE M1A3 THE WAY IT SHOULD BE

 

[Damian]

Above article is nothing more than a private person opinion. The fact however is that most of NATO, besides British, sees rifled guns as obsolete and do not want to further use them.

Americans after inducting and redesigning German Rh-120 in to M256, never designed any new rifled gun in 120mm calliber or bigger for MBT's. All new guns like XM291, XM360 and XM360E1 are smoothbore, you can find it in documents on DTIC archieve.

Also all new developd ammunition is for smoothbore guns.

There is no technical, or economical reason to adapt rifled gun, not to mention that opinion of that person that rifled is more versatile is not truth and was based merely on ammunition not the gun itself. At time when US would test British rifled gun, it had HESH ammo (among some other types not inducted in to service), in case of smoothbores due to NATO doctrine to stop massive Soviet tank hordes, developers focused firstly on developing purely anti armor ammunition like APFSDS and HEAT, other types like HE had low priority and their development started in 1990's.

Besides this progress in technology, huge number of different ammunition types is not nececary, for example in USA, four types the M830, M830A1, M908 and M1028, which are HEAT-MP, MPAT, HEOR and Cannister (huge shotgun) types of ammunition, will be replaced by single type, the programmable AMP HE round.

And this is very reasonable, tanks on avarage takes around 40 rounds of ammunition, if you need to load several different types of ammunition, you efficently reduce quantity of each type to several rounds only, in case of only two types, you can more efficently distribute space for APFSDS and HE, for example like 20/20, 25/15 or 30/10.

Oh and one more thing, people that were witing back then to ARMOR Magazine, were in great numbers complete amateurs, not understanding even basics of tank design in their own country + there were trolls like Mike Sparks trying in each letter to force US Army to give M113 a name "Gavin". After that as far as I am aware, redaction of ARMOR Magazine, stopped to place so many letters from avarage people.