120mm vs. 125mm

rattler said:
The only sensible comment, IMHO.. :) :mrgreen: :jump: :drunkb:

The rest, its all really missiles nowadays (in this kind of CW scenarios).

Rattler
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That's not true. When 2nd BCT, 3rd ID was pushing towards Baghdad in 03 they encountered quite a few armored vehicles that were comoflagued so effectively that they could not be seen or engaged until they got tanks in there to actually get eyes on the targets and fire main gun. People don't give the Iraqis enough credit for how tenaciously they fought for Baghdad because we just smashed them. Read the book Thunder Run by David Zucchino and you will learn a lot about the fight (to include the worth of the tank main gun). Hell, 4-64 AR shot over 60 main gun rounds in one day.
 
tank main guns remain the most powerfull direct fire elemnts in the modern warfare. In Lebannon some crews fire as much as 200 rounds during the war in 2006, and there were no tanks on the others side. I dare anyone to give me another system that can produce the effect of a 120 or even 105 tube firing HEAT/HESH/APAM/Flechette at infantry with pinpoint accuracy.
 
Guys, back to the original topic ... 105mm vs. 120mm vs. 125mm (vs. 150mm)

Isn't the ultimate "kill vehicle" for heavy armor still a DU penetrator from a sabot round which is 30-50mm in diameter? If so, the sabot (or "shoe") can be anything from 90mm all the way up to 150mm or more ... it shouldn't matter too much.

What about a 105mm round that has 50% greater cartridge capacity and velocity potential? Surely that would be a giant slayer ... although such high velocities usually mean a short tube life. :(

Now, if the best warhead is HEAT or HESH, then diameter is more important to warhead performance and bigger is usually better. But then, the biggest obstacle is to get such a large diameter round to perform well ballistically and hit targets thousands of meters away.

My guess is, something around 120mm - 125mmm is about optimal (virtually no difference from a theoretical point of view) given the performance of what's out there now and what seems to work.
 
The diameter is important. The reason is that a larger diameter gun theortically has the abilety to fire the penetrator at higher speeds. There is only so much you can add to the cartridge in length before its too long to be practical in what is a tight turret anyway. Thats why 120mm guns do have higher velocities than 105mm guns.

But as been mentioned here, there are issues with simply enlarging the gun. A 120mm L55 such as the one in the Leopard 2A6 is 6.6 meters long. Guns over 7 meters long create serious issues with sight adjustment, turret control etc. So a 140mm gun would have to be a L50. The length in calibers of the gun has a great influence on preformance. A long barrelled 100mm can out preform a short barreled 155 in some aspects.

But again, between 125mm and 120mm the diffrence is small enough that it is almsot pointless. with a 5mm diffrence penetrator length and materials as well as design is far more important and influencial.

I am still waiting for ETC guns to be fielded, as they will allow the 120mm to out preform even a 140mm in muzzle energy and so will change the entire situation.
 
Sherman, I was thinking increasing the cartridge case width to increase capacity and not necessarily make it longer ... although Think of the various .30 cal rifle cartridges from .30 Carbine to .300 Weatherby Magnum. Diameter is the same ... but the power (in foot-pounds) of the Weatherby is several times greater.

If you take the current 120mm round, neck it down to 105mm and cap it with a projectile that is similarly downsized, velocity would increase (a bit).

An increase in either direction would, of course, increase the size of the breech and make fitting the weapon on some platforms difficult (like you said) ... not to mention the loader mechanism and reduced ammunition storage.

In short, you can't get sumthin' fer nuthin.' :wink:

I guess the point of the matter is that some people assume that cartridge capacity is a constant ... which it is not ... and really thoughtless people just assume that larger is always better. Think of the German 88mm guns versus the Soviet 152mm in WWII.

Yes, ETC technology looks promising ... but it doesn't seem to address the diameter issue ... just the ignition issue (which is a big one, I understand).
 
it is a huge issue because if the ignition is done in a way that creates a longer and more evn pressure curve youcan dramtically increase the muzzle speed.
 
Bror Jace said:
If you take the current 120mm round, neck it down to 105mm and cap it with a projectile that is similarly downsized, velocity would increase (a bit).
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Ah, but some smoothbore rounds already act like this. MPAT and MPAT OR rounds as well as the SABOT on the 120mm rounds (US issue) are not the same size as the tube. MPAT OR is very similar to HEAT but has a 3 petal sabot(300 m/s faster than a HEAT round due to the smaller round). Most people are aware that the SABOT rounds are much smaller than the tube diameter but the same is true for the other ones. I would think there would have to be a limit on how large you could make a HEAT round and still hit a moving target at distance since they are not the most aerodynamic thing out there and fly like a brick. The fact that the US tank rounds are one piece means the penetrator (only on service ammo) comes all the way down into the casing and almost to the tailcap (or stub base/ aft cap to tankers). This gives you an enormously long penetrator without increasing the overall size of the round. Tanks that have a 2 part round (ammo goes in, then powder) do not have this added benefit. I love to load on the M1 and I'm a big fan of the one piece round. Take a look at a service SABOT round cross section and you'll see what I mean (Google images search M829A3. Make sure you look at the new A3, not the older smaller ones)
 
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19kilo30K4 said:
When 2nd BCT, 3rd ID was pushing towards Baghdad in 03 they encountered quite a few armored vehicles that were comoflagued so effectively that they could not be seen or engaged until they got tanks in there to actually get eyes on the targets and fire main gun. People don't give the Iraqis enough credit for how tenaciously they fought for Baghdad because we just smashed them. Read the book Thunder Run by David Zucchino and you will learn a lot about the fight (to include the worth of the tank main gun). Hell, 4-64 AR shot over 60 main gun rounds in one day.
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Thanks, missed not only the book but the info as such.

With you on the Iraqui resistance, not at all unprofessional, but inadequate.

Rattler
 
Just a quick question and from ignorance I know it could sound dumb, but would be possible to mount the GAU-8/A Avenger gun of the A-10 Thunderbolt in a tank? Had it been ever considered? Would it be worth? Would be a way to use it's anti-tank capabilities.
 
19kilo30K4, so the SABOT and MPAT rounds are essentially squeezed down as they travel through the tube? OK, that makes sense ... if for gas-sealing alone.

"I would think there would have to be a limit on how large you could make a HEAT round and still hit a moving target at distance since they are not the most aerodynamic thing out there and fly like a brick."

Yup, I said this above. :thumb:

"would [it] be possible to mount the GAU-8/A Avenger gun of the A-10 Thunderbolt in a tank?"

That would be hysterical! Still, I would think you need a number of 30mm hits to take out an MBT, so you have to get into position and expose yourself longer to squeeze off an effective burst. And then, with a dotted line in the sky pointing back at your position, everyone within 15 miles would know where you were. :o

While a tank such as you envisioned would be entertaining in a videogame, one precision shot from a larger tube makes more sense in the real world of armored warfare. ;)
 
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Bror Jace said:
"would [it] be possible to mount the GAU-8/A Avenger gun of the A-10 Thunderbolt in a tank?"
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That would be hysterical! Still, I would think you need a number of 30mm hits to take out an MBT, so you have to get int position and expose yourself longer to squeeze off an effective burst. And then of course, everyone within 15 miles would know where you were. :o
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Understood. :thumb:
I thought that a simple burst would be enough to take out an MBT.
Bror Jace said:
While a tank such as you envisioned would be entertaining in a videogame, one precision shot from a larger tube makes more in the real world of armored warfare. ;)
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:lol: :lol: :lol:

All clear so. :thumb:
 
Thinking s'more about this in the past week, I wonder how the 30mm shells would do against the SIDE of an MBT as opposed to coming in (mostly) from above (where armor is universally thinner) like they do when fired from an A-10. Still, I bet the angle coming in is very shallow ... rarely more than 25-30 degrees ... so the hits are already more side than top. The angle would, however defeat much of the sloped armor's advantages.

Also, you have to add the plane's velocity to the muzzle velocity of the cannon. The conversion is 1mph = 1.467 feet per second ... so add about 500fps to the 3,500fps published muzzle velocity ... another 15%.

Not sure if either factor is significant ... but they crossed my mind.
 
cisco said:
>150mm are coming, Koreans have an option to build it into their tanks, Americans and Germans are quietly considering a new generation of tanks with a 150mm main gun, Russians too though in their case its more of wishfull thinking.<

Hope Krupp (I think its Rheinmetall now) didn't lose the blueprints for the Big Bertha. Ansd maybe we can mount some 400 mm guns on the ne frigates. The MONARC Project looked quite promising, but still a small Calibre if we want to do it as bigger as better way.
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No, the U.S and NATO is not considering a 150mm gun, 140mm was tested in early ninties as part of a joint ETC program that involved U.S, UK, France and Germany. The 120mm will be around for at least the next decade or two due to maingun capabilities.
 
19kilo30K4 said:
Well, the diameter doesn't make much of a difference when talking about penetration VS other tanks. Have you ever seen our service SABOT rounds? It's a hell of a lot smaller than 120mm. When speaking of ammunition penetration VS tanks, the length of the DU penetrator is what's important. As most of you probably know, our APFSDS ammo discards the SABOT "petals" once it leaves the tube, so 120mm, vs 125mm is not as important as you may think. The only rounds we have that take up the full 120mm is the HEAT and the canister. The others (MPAT, MPAT-OR, SABOT) have discarding petals, so the 120mm size is not really even descriptive of the round. The major difference is theirs is rifled for accuracy and ours is fin stabilized. All this talk of increasing sized cannons neglects the fact that we put a 105mm gun on the M1 before the Germans showed us just how accurate the M256 can be. We most certainly have a more diverse array of 105mm ammo (APFSDS, APDS, HEAT, HEP, WP, APERS) and that is especially true since the revival of the 105mm on the Stryker MGS. Our guns are getting bigger? Then why does the newest gun system the Army has only have a 105mm? Because that's all it needs, and that's all it can handle.
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As you know Iron Chariot rider that you need energy and mass for target penetration when using KE penetrators, for extended main gun ranges caliber size does matter when encountering modern day armor.

Also just a minor correction, Russians use smoothe bore tubes also.
 
SHERMAN said:
The 105mm was fine for its time, that time is the 1960s. Today, a 105mm would have a hard time against any real opponent. APFSDS-DU goes a long way to even the match but still, a 105mm just dosent have the abilety to punch a hole in the frront armor of tanks designed from the 1980s and onwards. A Merkava Mk 4 would seriously laugh at a 105mm round, unless someone came out with somthing new in the last year:)

There is no major diffrence between 125 and 120, the question is the design of the penetrator adn the materials, as well as the length of the gun itself. A 55 calibers long 120 with DU rounds is certinly more lethal than any 125mm i know of.

As far as future guns I am not sure if size is the solution. I hope they field ETC guns in 15 years time. If it takes longer they should look into 140mm as an intrim solution. Loading 140mm rounds would probably require an automated loader which, exept for the Leclerc, most western tanks dont have as a policy...
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Do not sell the 105mm short inregards to the MGS system, granted it is not the ultimate vehicle to engage heavies with but for ambush purposes I think that you would find that a 105mm M900A1 round will do some damage at close range engagements.

The Germans went to L55 to get out of the DU business, switched to Tungsten so stretch tube was needed, incase of emergency though L55 can fire NATO projectiles exception being UK projectiles. Rest assured that 120mm will be around for quite awhile, there is no justification for going to a bigger caliber just as it is not warranted for the U.S to switch to L55 gun tubes because of DU projectiles. Auto loaders have been tested in M1 series tanks, the switch will not be too painful. :tank:
 
Pale Rider said:
Also just a minor correction, Russians use smoothe bore tubes also.
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I'm sorry, I didn't specify. I was more speaking of other 120mm guns such as the L30 on the Challenger. I didn't specify that I meant Russians, but thanks for mentioning it so I could clarify. There's just so many vehicles with 120mm and 125mm weapons on them that maybe the name of this post should have been "2A46 vs M256" :smil:
 
Really there are only a few systems. The russian 125mm, the American 120mm and its clones/veriants, and the british 120mm...You could count the German 120mm L55 as the fourth maybe...
 
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