AI T-34 tank tactics not bad!!!

[Bone_Vulture]

Originally posted by YankeeDog:

This is one reason why some modern tanks, such as the M1 Abrahms, use smoothbore guns -- no spin to the shell = much higher HEAT ammo performance.

HEAT ammo for Abrams? I thought it only fired SABOT rounds, and the barrel was smoothbore since the extreme exit velocity and pressure would eat the rifling rapidly.

[Sergei]

Originally posted by Bone_Vulture:

HEAT ammo for Abrams? I thought it only fired SABOT rounds, and the barrel was smoothbore since the extreme exit velocity and pressure would eat the rifling rapidly.

It has HEAT but no HE.

[YankeeDog]

Yes, rifling wear is another reason for the smoothbore design.

Last I heard, HEAT was still the most-carried, utility round for the M1 -- used against lighter, less threatening armor (APCs and the like), or even against enemy MBTs at closer ranges where the accuracy advantage of the Sabot rounds is less important.

Also worth noting that the smoothbore design is part of what gives the Sabot round its extremely high accuracy -- the lack of spin makes it much easier engineer the sabot so that it peels away from the DU penetrator without disturbing the flight path.

Cheers,

YD

[DEY]

I think there is a little confusion here. Rifled barrels do one thing only, which is to make the projectile spin therefore stabilizing the round making it travel more accurately. It does not affect the outright speed the round travels at from the fire point to impact point, that depends on, 1)the shell propellant quality and quantity, 2) gun barrel length.

So the older HC ammo would only be helped by rifled barrels. I do believe that the longer barreled guns like those on the panther would likley had needed the shell charge tweaked, being that the round would likely hit a higher then liked velocity.

The reason tank guns are moving to smoothbore barrels is because some countries use special types of ammo in canister form, in the case of the US army their tank gun ammunition has moved from the old spin stabilized rounds to FIN stabilized and now to SMART munitions.

[YankeeDog]

Sorry, but you're a bit incorrect here, at least in terms on the value of HC ammo in high velocity, rifled guns.

While you are correct that, strictly speaking, velocity of the projectile has no effect on HEAT ammo performance (assuming the fuze is quick enough to detonate the projectile upon impact before it is deformed, of course), generally speaking, the higher the muzzle velocity of a rifled gun the more revolutions *per minute* the shell makes as it's traveling through the air (even though it may make the same number of revolutions *per meter* as a slower travelling shell).

Centripital energy is directly related to revolutions per unit time, not revolutions per unit distance of an object travelling through space. This is why HEAT ammo generally has crappy performance when fired from high velocity, rifled guns. Once again, the centripital force tends to unfocus and disperse the plasma jet and reduce penetration. This is actually the same physical effect that causes spinning objects to throw matter outwards when they disintigrate -- imagine a rapidly spinning dinner plate dropped on the floor. When it shatters, the fragments fly outward across the room. The same thing happens to the molecules in the plasma jet of a rapidly spinning HEAT projectile. They tend to fly outwards due to the centripital energy, dispersing the jet.

This effect is well documented -- any decent book or treatise on armor penetration should include info about it.

No argument, though, that there were other reasons for going with a smoothbore gun in the M1 - better performance of HEAT ammo was just one factor.

Cheers

YD

[DEY]

Never once have I ever seen or heard of that term in regards to ballistics. It appears you may be using an scientific term out of context here. If you have a web site that does use this physic law in regards to ballistics I'd like to see it.

modern tank guns are smoothbore, not rifled. This is because practical rifling twists can only stabilize projectiles with a length to diameter ratio of up to about 5:1, and also because the rifling adds friction and reduces the velocity it is possible to achieve. To get the maximum force on the smallest area, anti-tank rounds have aspect ratios of 10:1 or more. Since these cannot be stabilized by rifling, they are built instead like large darts, with fins providing the stabilizing force, negating the need for rifling. These subcaliber rounds are held in place in the bore by sabots. The sabot is a light material that tranfers the pressure of the charge to the penetrator, then is discarded when the round leaves the barrel.

The above is from here

Ballistics

It's from the Terminal ballistics section, there is lots of interesting stuff here everything from "Physics of trajectories" to "Newtonian mechanics"

[YankeeDog]

Well, here's a really quick reference I found in 5 seconds on google. I have better ones at home in books:

"High explosive anti-tank (HEAT). Designed to detonate a shaped charge on impact. At detonation, an extremely high velocity molten jet is formed. This jet penetrates a large thicknesses of armor, continues along its path, and sprays molten metal inside the target. If the jet hits an engine or ammunition, it may start a fire or cause an explosion.

Rotation reduces the effectiveness of HEAT rounds, so spin-stabilized projectiles usually do not use HEAT warheads. [emphasis added]

HEAT rounds generally range in size from 60 to 120 mm. As a rule of thumb, a HEAT round can penetrate armor up to five times the warhead's diameter (e.g. a 100mm round can penetrate 500mm). Tanks, anti-tank weapons, and automatic cannons usually use these types of projectiles."

from

weapons effects

The original discussion here was about HEAT rounds for the PzIV. My point is, 75mm HEAT rounds would have crappy performance in 75mm/L48 guns. Therefore, late war, PzIV(lang)s would be, generally speaking, better off with AP ammo.

I don't disagre at all with all of the other points you make about the smoothbore gun and it's advantages as an anti-armor weapons system. My point is simply that another positive attribute of smoothbore guns is that they offer much better HEAT ammo performance because the projectile does not spin, and that furthermore this is probably one of the major reasons why the M1 120mm smoothbore uses HEAT as its bread-and-butter Anti-armor round. Another reason would probably be that HEAT, unlike kinetic AP, works pretty well as a dual purpose round -- it has enough explosive power to damage soft targets as well.

Regards,

YD

[Sergei]

Originally posted by YankeeDog:

Rotation reduces the effectiveness of HEAT rounds, so spin-stabilized projectiles usually do not use HEAT warheads.[emphasis added]

<s>I'm sorry if I'm asking a stupid question here, as I just woke from an evening nap and my brain is still sleeping, but does that make sense? ATGM's and AT rockets are spin-stabilized and I don't think they rotate that much anyway.</s> Woops, Herr Spindoktor sez: "I belief we need to stabilize zis Finn or do zomefink!"

Hey DEY (I just had to say that ), I and Gary finished the Hungary Pains scenario and left our reviews in the discussion, did you notice? We loved it!

[ December 14, 2004, 08:03 AM: Message edited by: Sergei ]

[DEY]

I just run across this again that refreashed my nogin that the germans did indeed have 88mm HC for the tigers, know as "hollow-charge Gr.39HL round".

As I stated rifle barrels only twist a projectile as it travels through the barrel, therefore making it more stable and thus more accurate. If it does anything it slows the projectile down as it travels through the barrel.

Newer heat ammo would indeed have problems being fire from a rifled barrel because of that detonator rod on the head of the round. Older gen1 HC I believe was enclosed in a cone shape projectile like HE and AT ammo.

It's been a long time but any newer heat I recalled had some sort of fin stabliztion.

Sergi, any Anti Tank Guided Missile (ATGM) or AT-rockets I know about are all fin stablized and can be launched from only smooth bore gun devices.

Thanks for the playtest, I did leave comments.

[JoMac]

Originally posted by Kanonier Reichmann:

[QB] You don't need HC ammo when pitting Pz IV's against IS2's in the game. Just shoot at their frontal aspect & you'll achieve a turret penetration on the IS in no time using standard ammo. :eek

Its unbelievable, i can even KO the ISU 152-122 tanks in the frontal aspect with a pak 40, go figure.

[Bone_Vulture]

Originally posted by JoMc67:

Its unbelievable, i can even KO the ISU 152-122 tanks in the frontal aspect with a pak 40, go figure.

What's so odd about that?

... And I believe some of the posters here are confused between spin stabilized and fin stabilized.

[DEY]

Originally posted by Bone_Vulture:

And I believe some of the posters here are confused between spin stabilized and fin stabilized.

Well BV, maybe you could enlighten us.

I have found some other claims that YankeeDog made about spinning Heat rounds being less effective, which I never heard before. But also I found that even in WW2 that the germans was able to counter the spin affect.

Adaptations to existing tank guns were somewhat more difficult, although all major forces had done so by the end of the war. Since velocity has little effect on the armor-piercing capability of the round, which is defined by explosive power, HEAT rounds were particularly useful in long-range combat where the slower terminal velocities were not an issue. The Germans were again the ones to produce the most capable gun-fired HEAT rounds, using a driving band on bearings to allow it to fly unspun from their existing rifled tank guns. HEAT was particularly useful to them because it allowed the low-velocity large-bore guns used on their numerous assault guns to become useful anti-tank weapons as well. Likewise, the Germans, Italians, and Japanese had many obsolescent "infantry guns" in service (short-barreled, low-velocity artillery pieces capable of both direct and indirect fire and intended for infantry support, similar in tactical role to mortars; generally an infantry battalion had a battery of four or six). HEAT rounds for these old infantry guns made them semi-useful antitank guns, particularly the German 150mm guns (the Japanese 70mm and Italian 65mm infantry guns also had HEAT rounds available for them by 1944 but they weren't very effective).

Quote from this site.

High explosive anti-tank

I hope you understand Yankeedog I didn't mean to come off sounding rude. I'm just trying to get the facts straight, for myself if anything.

[Sergei]

Originally posted by Bone_Vulture:

... And I believe some of the posters here are confused between spin stabilized and fin stabilized.

I shouldn't post when I'm gin-stabilized.

<font size="1">(That was specially for you, Bone.)</font>

[YankeeDog]

No problem, DEY. Engaging discourse is what we're here for.

If you're curious, the reason why rapidly spinning projectiles don't make good HEAT penetrators has to do with rotational momentum. The rules of Conservation of Momentum and Energy apply to rotational motion just as they do to linear motion. So when the HEAT projectile explodes and the contents of the warhead are converted from their solid state into a fluid plasma by the chemical reaction of the explosion, by the laws of physics the particles in the plasma must retain the rotational energy and momentum characteristics they had while solid (in addition to the new energy and momenutum imparted by the explosive reaction, of course).

Since the forces holding the molecules of the plasma fluids penetrator are far weaker than the forces holding the molecules in the solid warhead together, the net effect is that centripital force "wins" and the plasma jet will begin to unfocus and "spin apart" as it travels forward in the jet. This, of course, reduces armor penetration dramatically.

So this effect applies to all shaped charge penetrators, modern and WWII-era.

If you want a detailed experimental examination of the subject, I would reccomend the following article from the Journal of Applied Physics:

Singh, Sampooran: Penetration of Rotating Shaped Charges, Journal of Applied Physics -- March 1960 -- Volume 31, Issue 3, pp. 578-581.

You are quite correct, though, that the Germans had begun to develop solutions to this problem in WWII, most notably the use of a free-rotating driving band on the HEAT projectile. This same solution was also used in some post-war HEAT ammunition types. Offhand, I believe the French were using a free-rotating driving band on a 105mm HEAT projectile for a while; there are probably others.

The problem with this approach is that if only the driving band of the shell is rotating, some of the stablizing effect of spinning the shell is lost, so you end up with a less accurate round. One way to get around this is to actually create a spinning outer sheath, rather than just a driving band, with a non-rotating inner core that contains the HEAT charge. Here, though, you're sacrificing at least some shaped charge diameter, which of course will reduce your penetration.

However, returning to the original issue of HEAT ammuntion for 75mm/L48 guns in WWII, given shaped charge technology of the period, and the techical issues surrounding adapting a HEAT projectile to a high-velocity gun like the 75mm/L48, I really doubt that firing HEAT through the L48 would have garnered Axis tank crews any net gain in armor penetration. Even if the Germans managed to solve all of the technical issues surrounding firing HEAT from a high velocity gun and get perfect performance of the available HEAT ammo when fired through the 75mm/L48, the best 75mm HEAT the Germans produced during WWII (available only very late war, and then in limited amounts) is superior to plain 75mm/L48 APCBC only when striking highly sloped plates, and/or at very long range. In other situations, the APCBC is as good or better than the HEAT.

Again, if you're talking about shorter-barrel, lower-velocity 75mm guns, things are totally different.

Cheers,

YD

[Bone_Vulture]

Originally posted by DEY:

Well BV, maybe you could enlighten us.

I'm not up to date with modern armor warfare munitions, but don't the subcaliber rounds have actual fins to keep the round stable while in flight, since it isn't given a spin around its axis with the rifling?

And spin stabilized is just that, the round is given a spinning momentum with the rifling to keep its head pointing to the direction of movement.

Originally posted by Sergei:

I shouldn't post when I'm gin-stabilized.

<font size="1">(That was specially for you, Bone.)</font>

IM ABOT 2 BRAKE!!!1 :mad:

[DEY]

Originally posted by Bone_Vulture:

I'm not up to date with modern armor warfare munitions, but don't the subcaliber rounds have actual fins to keep the round stable while in flight, since it isn't given a spin around its axis with the rifling?

And spin stabilized is just that, the round is given a spinning momentum with the rifling to keep its head pointing to the direction of movement.

I'm not all that bright a fellow, but hasn't all that stuff been around noted in mine and other peoples post's already.

Yankeedog I agree there is evidence that a spinning heat round is LESS effective, but how less is an unknow factor here, for any of that early Gen1 stuff anyway. Also I for one don't know how well that DRIVING BAND fix turned out for the germans, as far as I can see it was a fairly effective change.

Also I agree that HC ammo is an somewhat quirky ammo type to get delivered on target effectively.

But it was used in many guns including and by the Romanians at least in their T4 AFV with success.

When that 122mm gunned JS2 hit a Pz4, it wasn't a pretty picture, there are cases where the round penetrated through the front and the whole backend was blow right off, throwing the engine several meters away from the AFV.

That 75mm-L48 gun can kill Js2 tanks, but it's very rare to achive one shot kills with AP ammo, but with HC ammo it can get one shot kills, IF, the conditions are right. So I'm sure that if you was a Pz4 crew you would've liked to had a few of those rounds in your tank.

Here is a small description on the driving band.

Driving Band info

Here is a couple of sites I run into the last few days, there is some interested info here.

GUNS & ARMOR

Large Cal Guns

120mm Tank Gun KE Ammunition Tanks

It's been interesting.

[YankeeDog]

Do you have any references suggesting that 75mm HEAT was more effective at knocking out IS-2s than 75mm APCBC?

The reason I ask is that, as I mentioned, on paper 75mm HEAT round isn't really any better in terms of penetration or behind-armor-effect than the 75mm APCBC in most combat situations.

There could be an explanation, though. For example, it could be that something about the IS-2's internal layout made it more vulnerable to KO by HEAT. I don't know. But I'd be curious to read any info suggesting that HEAT was dramatically more effective than other ammo types.

And yes, on the other end of the stick, a PzIV penetrated by a 122m AP round would have a very low chance of survival.

Cheers,

YD

[DEY]

All I have at the moment is a forum thread in regards to a romanian tank ace Lt. Ion S. Dumitru, who had made Js2 kills with a T4 firing HC ammo.

Also there is statements that the romanians did equip their T4's with at least 5 rounds of HC.

The Hungarian Zrinyi II AFV is or at least was a highly regarded close support and AT AFV and the only official AT ammo this AFV had was HC, though it was in 105mm calibre.

Also food for thought is to ask yourself how many Js2's meant their doom from Panzerfaust's and schreck's