120mm vs. 125mm - Page 3




 
--
 
September 5th, 2009  
19kilo30K4
 
 
Quote:
Originally Posted by rattler
The only sensible comment, IMHO..

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

Rattler
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.
September 5th, 2009  
SHERMAN
 
 
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.
September 5th, 2009  
Bror Jace
 
 
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.
--
September 5th, 2009  
SHERMAN
 
 
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.
September 5th, 2009  
Bror Jace
 
 

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.'

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).
September 5th, 2009  
SHERMAN
 
 
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.
September 5th, 2009  
19kilo30K4
 
 
Quote:
Originally Posted by Bror Jace
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).
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)
September 5th, 2009  
rattler
 
 
Quote:
Originally Posted by 19kilo30K4
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.
Thanks, missed not only the book but the info as such.

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

Rattler
September 5th, 2009  
Titanium
 
 
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.
September 5th, 2009  
Bror Jace
 
 

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.

"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.

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.
 


Similar Topics
120mm M1028 Canister