Modern tankers explain, please....

[John Kettler]

This question has driven me nuts for quite some time, albeit intermittently. The question?

How is it that what sure looks to me like a shot trap on the front of the entire M1 tank family, despite being plainly visible, never seems to rate any discussion at all? I'm talking about the gap running from the underside of the turret down to the turret ring and from the glacis plate up to same. If early Panthers could be killed by bouncing projectiles off the lower portion of the mantlet and through the thin hull top armor, then why couldn't fire be directed at the underside of the front of the M1 turret to send HVAPFSDS screaming into the turret ring? For that matter, why not just aim RPGs and ATGMs squarely at the turret ring? Am posting this here because this is where we have not only a concentration of modern warfare grogs, but also serving and former tankers.

Regards,

John Kettler

[flamingknives]

The answer is that modern AP rounds, be they HEAT or APFSDS*, is that they simply do not bounce. If they are diverted from their line of flight in any way, their penetration capacity drops massively. In the same way, although the turret front for the Leopard 2A5 and 2A6 looks even worse (arrowhead applique armour) it simply doesn't matter because modern armour-piercing ammunition doesn't work like that.

Allied to this, the amount of armour on even secondary locations on a modern MBT is enourmous compared to WWII tanks. Even the roof will match the frontal armour of most late-war tanks. AFAICT, the turret ring itself is still a fairly massive bit of metal - after all, it supports a 20 tonne turret and almost the same amount of recoil force. If you're close enough to go for the turret ring, you might as well go for something bigger and less well armoured, like the turret side or lower hull.

*HV isn't necessary when describing APFSDS. I can't think of anything other than a High Velocity fin round

[John Kettler]

flamingknives,

I appreciate the explanation, but I'm not sure I buy it in toto. At close range, for example, why could the turret ring not be targeted directly? After all, the projectile is only about an inch in diameter, whereas the gap looks to be the best part of a foot or more vertically. If Wittmann with a stubby StuG could target a T-34's turret ring at tactically useful ranges, why couldn't the same thing be done, with vastly flatter shooting weaponry, in MOUT today?

Isn't the gun on the Challenger II rifled? If so, is the projectile fired a despun standard one like

what the M1 and Leopard use or a finless variety?

If the latter, it would appear that the projectile couldn't be APFSDS.

Regards,

John Kettler

[flamingknives]

I didn't mean to imply that the turret ring could not be targetted directly, but that such a feat wouldn't really provide the returns necessary to justify such accurate shooting.

The gun currently mounted on a Challenger 2 is a rifled L30 gun.

The L30 is the designation, not the German standard of identifying barrel length. The barrel is closer to 55 calibres long. The CHARM 3 sabot includes a slipping firing band, so it allows an APFSDS projectile. Other ammunition natures are HESH (HEP in US service nomenclature) and smoke.

[John Kettler]

flamingknives,

Seems to me it wouldn't take much to distort or wedge the bearing race badly enough to jam the turret. It's been done before with mere MG bullets during WW II.

Roger on the gun designation, rather in the mode of the old L7A1 NATO standard 105. Very much appreciate the clarification on L30 ammunition design!

Regards,

John Kettler

[flamingknives]

Roger on the gun designation, rather in the mode of the old L7A1 NATO standard 105. Very much appreciate the clarification on L30 ammunition design!

Well, it's a common system for all British Weapons systems.

Hence the 105 light gun is the L118, the SA80 is the L85 etc.

The turret race is going to be harder to jam than WW2 components too. The traverse mechanisms are designed to rotate that 20 tonne turret at something like 90 degrees per second or faster, so there's a fair amount of power there. I don't think that it's too much of an issue, since M1s have been hit plenty in Iraq, and it hasn't shown up as a weakness.

[jjhouston]

Competent tankers are going to be either moving or resting in a turret or hull defilade, the 'gap' won't be visible. And if it was, your gun tube would have to be at the exact same elevation to slip a penetrator through it. And you'd have to be close enough to a tank that can successfully engage first round kills at a couple miles distance in order to aim for the gap anyway.

Check these guys out for serious armor questions:

http://63.99.108.76/forums/index.php?act=idx

[M1A1TC]

From US tanker point of view, we are trained to fire center mass of a target. It is hard enough to hit a stationery defilade tank, even harder a moving one. We mostly engage at very long ranges, and using thermals, the targets appear as small white(hot)squares - or black squares, if you so prefer. Some tankers always use thermal sights, even during daylight.

Most armor versus armor engagements are over within

30-40 seconds. You simply do not have time to aim for turret rings or anything else.

[MikeyD]

I think John Kettler's concern is if you look at an Abram's 'center of mass' that's precisely where the seeming shot trap is! From the forward edge of the highly angled hull roof to the bottom of the turret front. It just looks as though anything that hits in that area will skip into the shot trap between the turret and hull. I believe on the latest Leopard II upgrade they've added a bit of extra protection in that area. They did the same for the old Stillbrew Chieftains too.

Of course, if you've ever seen a photo of an Abrams turret under construction the inner shell does not overhang the turret ring at the front. Its actually angled back rather sharply. It's the spaced composite armor package that overhangs. That may make all the difference. Still, I'd hate to be a driver if a big HE round gets wedged between turret and hull just over my head.

[flamingknives]

Modern AT rounds do not skip, bounce, ricochet or polka with anything but a small fraction of the penetrative power they started with.

[MikeyD]

...which is why I mentioned HE going off under the shot trap. There's also the theoretical threat of ATGMs glancing off the upper bow and wedging under the turret overhang, past the special armor.

Now that I think of it, isn't APFSDS a bit MORE likely to skip? I recall a famous photo of a Syrian T-62 with an amazing high angle penetration to the round gun tube. The consensus at the time was that it was an old 105mm APDS kill, not the (then first generation) APFSDS because the APFSDS would've skipped.

But hey, that's an anecdote about old generation rounds. Might have nothing to add to the current debate.

[flamingknives]

An APFSDS penetrator may glance off, but it isn't going to skip and be anything like as effective - it would break up into a shotgun-like scatter of broken fragments. It wouldn't possess the concentrated energy needed to go through any significant thickness of armour. The APDS penetrator, being much shorter, can yaw a bit, but for a long rod, it's my understanding that any yaw is catastrophic.

As for HE, there's not much that's an issue. A Conqueror (1950s era heavy tank) was hit repeatedly with a 5.5" gun firing HE. The only damage done was when the driver's hatch (quite thin) was blown open by a hit to the underside of the mantlet (due to a loose catch) allowing blast and fragmentation into the fighting compartment. The front armour was 120mm at 60 degrees from the vertical, plain RHA and with no spall lining.

[rleete]

Originally posted by flamingknives:

Modern AT rounds do not skip, bounce, ricochet or polka with anything but a small fraction of the penetrative power they started with.

Why do you hate the Polka so much? And what about the Mamba?

[flamingknives]

The Mamba's OK, I guess, but the polka! Uggh!

It takes me back to 'nam, man. All the radio played, first thing in the morning and before dusk - Polkas! That Lt. Steve and "Frenchie" *shudders, eyes glaze over and faint noise of helicopters is heard in the background.*

[Jeff Duquette]

Originally posted by John Kettler:

This question has driven me nuts for quite some time, albeit intermittently. The question?

How is it that what sure looks to me like a shot trap on the front of the entire M1 tank family, despite being plainly visible, never seems to rate any discussion at all? I'm talking about the gap running from the underside of the turret down to the turret ring and from the glacis plate up to same. If early Panthers could be killed by bouncing projectiles off the lower portion of the mantlet and through the thin hull top armor, then why couldn't fire be directed at the underside of the front of the M1 turret to send HVAPFSDS screaming into the turret ring? For that matter, why not just aim RPGs and ATGMs squarely at the turret ring? Am posting this here because this is where we have not only a concentration of modern warfare grogs, but also serving and former tankers.

Regards,

John Kettler

Hi John:

APFSDS will ricochet like any other projectile – given the right conditions. Mostly this means very high obliquity attack angles. The probability of ricochet is increased or decreased by other factors such as impact velocity and the material properties of both the rod and target. Harder armor makes the likelihood of ricochet greater. Rod density and rod strength also play a part. Off-angle shots combined with inherent armor plate slope will also increase the likelihood of ricochet – compound impact angles. Lower striking velocity also increase the likelihood of a rod penetrator ricocheting. LRPs constructed from steel – ala the BM-1, or BM-2 or BM-6 are more likely to ricochet than WHA or DU LRPs. Aspect ratio of the penetrator will also influence the critical ricochet angle. Higher aspect ratios have higher critical ricochet angles. Modern WHA and DU rods you are looking at critical ricochet angles in excess of 70 to 80 degrees – again depending upon the above variables.

Long rod penetrator ricochet actually results in the formation of a plastic hinge within the rod. As the rod begins to redirect into a rebounded trajectory, the rod bends along the contact area between rod and plate. A plastic hinge forms and propagates along the length of the rods from tip to tail as the rods direction is turned away from the surface of the target. So – yes the rod is subject to a large amount of stress and plastic deformation; fracturing of the rod into multiple segments can also occur.

As to the shot trap on an Abrams – I think the gap between the bottom of the turret and the glacis is required – at least partly so – to allow the turret to traverse completely around the hull. The rear deck is raised considerably above the elevation of the glacis, so this gap actually becomes pretty tight between the front of the turret and the rear deck. Vision blocks and the drivers hatch also come into play. The frontal turret area that overhangs the glacis – as stated earlier -- is pretty much all part of the special armor package. Layers of steel, DU and ceramic by most accounts. Assuming a rod penetrator did ricochet off the highly sloping glacis of the Abrams, it is quite likely that the redirected trajectory of the rod would put the new impact location into the bottom of the special armor package – at a very awkward angle of attack for the rod. The rod may well be fractured\fragments after the ricochet. It would certainly strike the bottom of the turret armor at a lower energy state following the ricochet. However, given the right ricochet conditions it does not seem unrealistic to think that a rod penetrator could ricochet from the glacis and strike a very vulnerable area between the turret and hull. The probability seems low -- but it could happen.

I won’t attempt to defend or prove any of the above. I am simply regurgitating what I have learned from studying the subject of long rod penetrator ricochet. A number of studies were conducted by A. Tate on the subject of long rod penetrator ricochet. These papers are a good place to start any additional reading on the subject.

Regards

JD

[ July 10, 2006, 08:27 PM: Message edited by: Jeff Duquette ]

[Michael Emrys]

Originally posted by rleete:

Why do you hate the Polka so much?

Because it is egregiously stupid and just plain bad? And you love it, right?

And what about the Mamba?

If you mean the dance, it's called Mambo, you idiot. A mamba is a snake. If you are asking about the snake...I'll send you one. Be sure to hold the box close to your face when you open it so he can give his new owner a great, big kiss.

Michael

[Mannheim Tanker]

Originally posted by John Kettler:

At close range, for example, why could the turret ring not be targeted directly?

It is targetted. In fact, M1 tankers are taught to aim center of mass at any range, provided they can get a shot at it (i.e. the tank is not in a hull -down position).

edit: After reading through the whole thread, I see that at least one other tanker has already posted on this. As he points out, you aim for center mass, which corresponds with the turret ring. When I trained for gunnery, I was always told this was done in an effort to hit near the turret ring, but as M1A1 Tank Commander states, you're not explicitly aiming at the turret ring per se, just hoping to get a lucky shot in there. With an M1, however, most shots will blow through the armor whereever you manage to hit the target.

[ July 13, 2006, 07:50 AM: Message edited by: Mannheim Tanker ]

[M1A1TC]

Thanks.

I have different MOS now, but on my last gunnery my tank scored over 900

[John Kettler]

Thank you all for the most interesting and even learned responses. I've read and carefully considered what's been said, but I still don't see why, at close range, it shouldn't be possible to directly target the substantial gap between the underside of the M1's turret and the glacis plate, the junction of which happens to be the turret ring.

I sure wouldn't want to take a HEAT round there if I were in that tank, nor would I want an APFSDS hit. Am not sure what an HE detonation from 100mm up might do in that same place, either.

Regards,

John Kettler

[flamingknives]

I'd be more concerned about the ruddy great return with would give on ground scanning radar.

Targeting the turret ring still requires a direct hit - a HEAT or APFSDS round isn't going to rattle on in there. Even if they could bounce and retain a small fraction of their effectiveness, it would need a very acute angle. The turret armour angle is too steep and hitting the glacis would be a mean trick since it has a very small frontal area.

From the sides and rear, there are more profitable places to shoot at than the substantial turret ring.

I wonder how much effectiveness the M1 would retain if a jammed turret forced it to play S-Tank. It would retain elevation, and I imagine that fine track control is probably enough these days to get the main armament on target out to a good distance. Any track drivers care to comment?

[M1A1TC]

Its hard enough to fire the main gun in manual mode, without hydrolics. If the turret ring was damaged, it would pretty much put the tank out of comission IMO

I used to be a decent driver (only one track thrown in 2 years). If the tank is in hull down position, and has decent concealment, and firing on a stationery target, it is possible to line up a shot using main hull and manual elevation. Anything else....

[ July 14, 2006, 10:22 AM: Message edited by: M1A1TankCommander ]

[aka_tom_w]

"With an M1, however, most shots will blow through the armor whereever you manage to hit the target. "

Isn't that kind like a paradigm shift in thinking.

We may be used to thinking in WWII terms were this was only really possible with the German 88 at close range: "most shots will blow through the armor whereever you manage to hit the target."

So the whole aiming at the turrent ring in modern armour combat is completely irrlevant... (as posted).

"With an M1, however, most shots will blow through the armor whereever you manage to hit the target."

-tom w

[M1A1TC]

You are right, the SABOT will penetrate whatever it hits, but you are trying to have it go through an important system, and escpecialy crew compartment. When sabot penetrates, and leaves the tank, it creates a vacuum behind it, which sucks out the crew in small pieces

[Dogface]

ouch, that has to hurt.

[flamingknives]

Not as much as the same thing happening combined with any DU pulverised in getting through the front plate spontaneously catching fire.

Also, having seen the after effect of an EFP vs a 100mm plate, I'd have to say that being in an AFV that's just had its armour defeated would have to be pretty high on the top ten places I'd rather not be.