"Skipping" AT Rounds

[Pak40]

While talking to my grandfather about US vs German Armor, he told me about a tactic that allied gunners used to help defeat the thick german armored tanks. He said that some gunners would aim low causing the flat trajectory round to literally skip off of the ground and hit the undercarriage of the tank or the lower front hull which is much thinner.

I don't know how often this tactic was used and I've never read any book that mentions what my grandfather said. But since CM tracks rounds that glance off of armor I was wondering if this "skipping" was modeled in your real world physics.

[Guest Big Time Software]

Someone (maybe you?) mentioned this a few months back. Since we've got nothing more than anecdotal evidence to support it, we're not including it in CM. It's a tactic that might have worked on occasion, but it's a rather desperate one and probably quite rare and not generally effective. But if we come across definitive evidence we will change our stance on this issue.

Charles

[Pak40]

it could have been me... oops

[Guest aaronb]

As far as being a standard tactic, 'skipping rounds' may have been, and likely was, rare.

But, for accurately modelling the physics of the round after it leaves the barrel, accounting for small angle-of-incidence strikes will add realism.

- .22 caliber rounds are well-known to skip when striking water at a shallow angle.

- a standard tactic to hit a fugitive hiding behind a car is to shoot, at a shallow angle, at the pavement just in front of the car.

- large-caliber centre-fire rifle rounds that strike at a shallow angle (as when firing prone) will often rebound and go right over the berm (not like a richochet off a rock, because the rounds then travel one or more miles while a ricochet severely deforms the bullet and limits further travel). This causes grief for the range owner, and the bonehead who discharged his/her rifle while pointing it at the ground. Oh, and anyone in the wrong spot well beyond the berm.

- old-style cannon-balls were counted on to 'skip' and wreak additional havoc.

So, if an AP round misses its target, and strikes the ground shallowly, there should be some chance of reflecting the round back up.

[Guest Big Time Software]

In theory I am sure this is possible, but I would think in practice it would be almost impossible. First of all, a tank's gun is usually about 4-5 feet off the ground. Because of this the target would have to be a helluva distance to get a shallow "skip", or firing from a slightly lower elevation. And the land would have to be perfectly flat too, with the target nicely placed right at the exact spot. I would also think that a round that size would have a great chance of burrowing into the ground, much greater than a small arms round. Charles would know

In any case, but the overall answer will still be a "no" you can't skip AP rounds at enemy tanks.

Steve

[Fionn]

BTW US and Russian tank crews who spoke of skipping spoke of doing it ONLY on frozen roads.

SO, if you happen to be directly in front of a German tank which is advancing over a perfectly flat, uncratered road at a great distance from you then you can try skipping. In any other circumstance you can't.

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Fionn Kelly

Manager of Historical Research,

The Gamers Net - Gaming for Gamers

[Guest aaronb]

Well gents, I did explicity declaim that 'skipping' would be a useful battle tactic. I was thinking more of unintended consequences, the same as being in the path of a round that 'skipped' off the frontal armour of a tank, which CM does model. With the 3D nature of CM, even a flat hill behind a target might cause a skip.

It would make the battlefield a more interesting and dangerous place - perhaps to be modelled in CM2?

Steve: I'd be interested in Charles' opinion and/or research. When he puts his head up for air, that is.

Fionn: oddly enough, the 'skipping' circumstances you describe are approximated in the Stuart/KT battle from your AT gun article.

Thanks for the input.

[Herr Oberst]

In a similar vein, for the winter ops, on hard surfaces, do the mortars do (potentially) more damage?

[Edit #1: Upon rereading the post, alter the topic to include mortars and indirect fire artillery.]

I have read in multiple places that mortar rounds striking hard frozen ground are actually more lethal since there is less ground penetration and upward spray of fragments, less penetration = more horizontal spray of the fragments...

[Edit #2: Oh, and do the allies get to use the airburst artillery shells?]

[This message has been edited by Herr Oberst (edited 09-07-99).]

[This message has been edited by Herr Oberst (edited 09-07-99).]

[Fionn]

Aaronb:

Not really IMO since my battle occured in summer. Skipping only worked on asphalt surfaces in winter time from what I have read.. Didn't work in non-ice weather..

Still, though its a topic worth discussing. It's interesting even if not common

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Fionn Kelly

Manager of Historical Research,

The Gamers Net - Gaming for Gamers

[NCrawler]

Well, I can vouch that skipping rounds works (at least on concrete/asphalt). I've seen first hand a demo of an MP-5/40, full-auto, skipping the rounds up to knee-high level. Good for shooting at suspects on the other side of a car. Works real good with .12 ga buckshot as well...

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Jon Johnson

Steel Lightning Productions

[Dar]

- a standard tactic to hit a fugitive hiding behind a car is to shoot, at a shallow angle, at the pavement just in front of the car.

Gee, I would have thought the idea was to puncture the gas tank and get a fugitive flambé.

Dar Steckelberg

"Tastes like chicken!"

[This message has been edited by Dar (edited 09-07-99).]

[Fionn]

For small rounds maybe it does but would AP rounds behave in the same way? I'm no expert on this but I'm sure Charles would know.

Charles? Or rather, Steve, let Charles out of his "coding box" to answer this one will you?

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Fionn Kelly

Manager of Historical Research,

The Gamers Net - Gaming for Gamers

[NCrawler]

I'm sure that ANY projectile hitting a hard surface at the correct angle would "skip" so to speak. Ask anyone current/former military about firing tracers at the range. The cannon on the Bradley IFV does the same thing.

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Jon Johnson

Steel Lightning Productions

[Mike D]

******************

Warning this is a mini-Diatribe

Those w/ week stomachs or an affinty

for physics should probably not proceed. The rest of you, go grab

a beer and enjoy...........

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Here's my "professional" engineering opinion.

Note that I'm no ballistics expert by any means, so take this for what it's worth. (i.e. probably not much )

I think they would behave different just because of the fact that the tank gun is a lot higher off the ground. Take a main tank gun that is 2-3 meters off the ground vs. an infantryman w/ a rifle about 1 m. of the ground. Assuming both fire level w/ the ground and neglecting air resistance they are both going to follow a perfect parabolic path away and downward from the firing gun. However, since the tank cannon starts at a higher elevation it is going to be pointed more downward into the ground when it strikes than the rifle bullet. It's tendency to skip, therefore, is going to be markedly less than the rifle bullet. As many have said, it would probably require a hard asphalt/concrete surface to make a tank cannon round skip and even then depending on the circumstances it might not do much due to deformation from impacting the ground affecting the shape of the projectile to the point that the aerodynamic characteristics are largely ruined. In other words it wouldn't fly as far or straight as compared to if it hadn't hit the ground. Furthermore, any change in shape of the projectile tip could likely affect it's ability to penetrate the enemy tanks armor even if it did manage to fly straight enough after skipping off the ground to hit the enemy tank. Next, grazing the ground will also reduce the total kinetic energy of the projectile which will also reduce it's armor penetration capability. Finally, striking the ground might just set the round off prematurely.

Also, I believe if the gun is fired at anything but a position level w/ the ground (again neglecting air resistance) that the angle of impact with the ground simply gets worse. If the enemy tank was closer than would be required to skip a round off the ground to strike it with the firing gun being level, then the firing tanks barrel would have to be depressed in order to score a hit. This simply adds to the downward angle at which the projectile strikes the pavement and makes it that much more likely that it will dig into it vs. skip off of it. Same holds true if the enemy tank is farther away and the tank barrel has to be elevated to fly far enough to strike the pavement in front of the enemy tank and skip off of it. The projectile will once again follow a parabolic path from exiting the gun to striking the ground. Only this time it will actually go upward, arc across the battlefield to a high point somewhere in the middle, then begin arcing downward toward the ground. The mere fact that it is following this kind of trajectory means that it too will strike the ground at a steeper angle than if it had been fired from a cannon level with the ground. End result in both cases is that such a round is more likely to burrow its way into the ground, pre-detonate, and will lose more kinetic energy and be more deformed than if it had struck the ground at a shallower angle (i.e fired from a horizontal gun).

Lastly all of the above assumes a perfectly level battlefield. If the ground in front of the enemy tank were sloped back toward the firing tank then the likelihood the shell would burrow into the ground would be proportionately greater with the degree of slope of the ground. If the ground sloped away from the firing tank the exact reverse would be expected.

Finally, all in all I think this kind of thing would be a pretty far fetched thing to pull off in real life. I'm not doubting that it did happen, just that a lot of variables have to be just right for it to work. So much so that in most situations it would probably be a pretty dumb thing to attempt to do. For one thing the probability of scoring a kill was probably pretty small. My guess would be less than 1%. The probability of damaging the enemy tank would probably be slightly higher, but you still have to hit it and skipping rounds off of pavement isn't the easiest way to do this. Just aiming straight at the enemy tank would probably provide a much higher probability of scoring a hit and also ensure that the full kinetic energy of the shell was available to do real damage to the enemy tank. Bottom line in my view is trying to do this can only accomplish 1 of 3 things:

1) Least likely scenario: Firing tank gets extremely lucky and skips a round off the pavement just right and manages to damage, or if extremely lucky, kill the enemy tank.

2) More likely scenario is firing tank wastes precious ammo trying this and accomplishes absolutely nothing.

3) Along with 2), while messing around trying to skip rounds off the ground to hit the enemy tank the enemy tank being fired at, or other nearby enemy tank whacks your a** and your dead.

All in all doesn't sound like a very wise tactic to me if you want my opinion. In any event I don't think BTS needs to bother modeling this sort of thing in the game since in the overall scheme of things the number of times this kind of thing was probably attempted is next to zero and the actual number of enemy tanks killed using such a tactic was probably even less.

Regards,

Mike D

aka Mikester

PS:

"Someone (maybe you?) mentioned this a few months back."

Charles,

Maybe you are recalling what I brought up some time ago regarding a show I'd seen on the Discovery or the Learning Channel. A P-47 pilot they were interviewing said that they knocked out many vehicles, including tanks (not sure how heavy a tank he was talking about) on paved roads back when he was stationed in the ETO. He described how they used the tactic of diving in at the necessary angle and aiming directly in front of the tank and letting go with all 8 .50 cal machine guns. The result was that the bullets richocheted off the pavement in front of the tank and easily penetrated the relatively soft under carriage armor of the tank. Apparently from what he claimed they killed quite a few tanks / other armoured vehicles in this manner. I suppose the fact that the plane probably came screaming in at a couple of hundred miles per hour in the dive adding some amount to the kinetic energy of the bullets made matters all the easier.

[This message has been edited by Mike D (edited 09-07-99).]

[This message has been edited by Mike D (edited 09-07-99).]

[Harold Jones]

I have seen tank main gun rounds skip into targets during gunnery, but it was not something you could do at will. Any more they don't give credit for those hits, they re-present the target and you engage it again. I would expect that even though skipping rounds is one of those things that people did or remember doing in combat that really wouldn't add anything to CM. If I remember correctly the armor models already allow for the odd one in a million shots. It's probably not worth the effort to code in skips specifically. Although it is kinda cool to watch a 120mm training HEAT round tumbling through the night after it deflects off something down range.

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If something cannot be fixed by hitting it or by swearing at it, it wasn't worth saving anyway.

[Guest aaronb]

Fionn: you're right, it is interesting! Esp. confirmation from Harold that it can happen even with HE-shaped rounds. I admit to being surprised by that. Perhaps Steve will release Charles long enough to comment

Mike D: to sum up your self-proclaimed diatribe, 'it's not a combat tactic'. Agreed. But, as Harold said, it's neat to watch the rounds carome off of things other than tanks (which is already modelled in CM). The other part of your message was about how high tank guns are... true if they're on a table top. Your reverse slope example shows how a nice shallow angle of incidence can happen. I'd be interested to hear from Harold about the circumstances of his 'skip'ing experiences.

Wow. I hadn't expected this much comment.

PS: Dar: "Tastes Like Chicken"? Are you allowed out of the house at night? Should you be?

[This message has been edited by aaronb (edited 09-08-99).]

[Dar]

Aaron:

Just want you to know that I've gone back to the electro-shock treatments since the medication wasn't working.

The streets are safe again.

Dar Steckelberg

[Dar]

Aaron had mentioned earlier in this thread that "skipping" cannonballs had been de rigeur at one time. Does anyone know when explosive shot and shell became used widely?

As I recall, from the first use of cannon through at least Waterloo (1815), cannon only inflicted casualties by striking the victims directly (whether solid-shot or canister). It wasn't until the American Civil War (or possibly the Austrian Wars of Succession?) that exploding shells were used to cause casualties by percussion and shrapnel.

Am I way off here, or is this somewhat accurate?

Dar Steckelberg

Anyone? Anyone? Bueller? Bueller?

[tss]

Dar wrote:

Aaron had mentioned earlier in this thread that "skipping" cannonballs had been de rigeur at one time. Does anyone know when explosive shot and shell became used widely

Once again I'm writing without my sources at hand, so take this with a large grain of salt.

There has been explosive shells for quite a long time, probably as long as there have been cannons. The earliest shells were hollow iron balls with a hole drilled in the surface. The shell was then filled with powder and a fuse was put through the hole. I'm not certain if the hole was otherwise sealed. The shell was then loaded to the cannon barrel with the fuse being upwards.

When the shell was fired, either the fuse was light before firing or it was counted on that the blast would set it on fire.

Those shells were _very_ unreliable, since you had to calculate the correct lenght for fuse, the impact might douse the fuse, or the whole thing could just blow up when fired.

The shells were mostly used in siege warfare, because it was not accurate enough for combat fields. With some luck the shells could be effective. There is one account that dates from the 30 year war (siege of Magdeburg, I think) where artillerists hit a trench with a shell killing lots of Catholics.

First incendiary rounds also date from the 30 year war. During sieges it became practice to put iron cannonballs into campfires and fire them red hot. The gunners tried to aim at thatch roofs and other inflammable structures. Sometimes the results were good but usually the defender could put out the fires without problems. Also, stuffing a red hot ball of iron on top of a gunpowder charge is not something that is fun to do...

IIRC, the first "modern" guns were designed by Krupp in 1870's. Once again, my sources are at home.

- Tommi

[Harold Jones]

Aaron said <BLOCKQUOTE>quote:</font><HR>confirmation from Harold that it can happen even with HE-shaped rounds. I admit to being surprised by that. Perhaps Steve will release Charles long enough to comment <HR></BLOCKQUOTE>

Sorry I forgot that not everyone knows that training HEAT rounds are inert. Didn't mean to mislead you. Modern HEAT rounds for the 120mm incorporate a shoulder fuze in addition to the nose fuze. This allows the round to detonate if it hits at a shallow angle, making it a somewhat useful anti-infantry and material round. This means that a service HEAT round would explode rather than skip.

[This message has been edited by Harold Jones (edited 09-09-99).]