AP vs HE - Short barrel vs Long

[tss]

Well, it seems that this thread should be put out of its misery but I like to point out one more thing:

If you are firing at soft targets with HE, high velocity can actually be a disadvantage. If the round travels too fast, it may bury itself too deep before detonating and most of the shrapnel effect is lost. How much this matters depends, of course, on the soil type and the fuse type.

Also, if you need both kinetic energy and exlosive charge, you are in any case better off using concrete-busting shells that are designed to penetrate deeply before detonating.

- Tommi

[Guest Pillar]

It seems really simple to me.

The advantage of slow speed HE is that it will not dig into the target too much before exploding, thus a wider area of effect.

The advantages of speed include penetration (if it is desired), accuracy, and naturally time to target.

So it simply depends on what you want to hit and why you want to hit it.

PS -- Whats "Apropos" mean? Honestly.

[Maastrictian]

Oh dear, what am I getting into?

Ok... physics, we've got physics. The arguement (or at least part of it) seems to be that the KE of the shell will add to the explosive energy of the shrapnel (also KE). I'm going to argue two points: 1. that the KE of the shell is only directed towards the ground so it is less important and 2. that the KE due to the explosive is greater anyway. I will note here that this arguement only applies to soft targets (infantry, guncrews, etc) not pillboxes. I would guess that these types of targets are the most common use of HE. I don't have any evidence to back that up, but it makes sence.

Ok, so imagine a shell striking the ground perpendicularly (this is not typical of most DF missions, but it makes it easier to draw pictures). The shell will explode as its front touches the ground. So the velocity of the shrapnel is the combination of the V of the shell (Vs) and the V due to the explosive (Ve).

..Ve..___..Ve

.<--..| |..-->

.......v.....

---------------

.......| Vs..

.......v.....

(little dots are for html/ascii graphics compatability)

Now lets assume that a given shell that stands .5 m high (big shell) can project killing shrapnel as far as 10m (these are random assumptions, but they seem reasonable. Think about how big an 81mm shell is and how far away it can kill someone). So a piece of shrapnel must be able to travel 10m along the ground before it travels the .5 meters to the ground. Hence Ve significantly (20 times) larger than Vs in our hypothetical example. Also, without the Ve our shell would simply be effecting a very small area. Even if every shot is right on target, we will only be killing one infantry man per shot with a shell without HE. And (this is the important bit) a shell cannot affect a radius greater than its length unless Ve is greater than Vs.

Finally note the 76mm gun on the Sherman and the 37mm gun on the Stewart. The stewart has a velocity of 844m/s while the sherman has a velocity of 793m/s. None the less, I think we can all agree that the stewart is less effective in both the HE and the AP role. Velocity is not the only factor.

--Chris

(edited for ascii graphics)

[This message has been edited by Maastrictian (edited 08-05-2000).]

[:USERNAME:]

<BLOCKQUOTE>quote:</font><HR>Originally posted by PzKpfw 1:

With that in mind I'd realy like to see that reply to the physics Prof post that you said, if you had time to someday you would respond to his points. Lets see that and the rebuttal and go from their if anyone bothers to contribute to this thread anymore .

Regards, John Waters

<HR></BLOCKQUOTE>

You the hostess here directing traffic?

First off, I am waiting for Norwood the alledged prof to clear up his "dot product" pontification. i think hes full of it.

What the hell are you rambling about? Are you mixing up philistines post with norwoods?

Now I see other people are contributing so get off the soapbox unless you can also.

Lewis

[:USERNAME:]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Maastrictian:

Oh dear, what am I getting into?

Ok... physics, we've got physics. The arguement (or at least part of it) seems to be that the KE of the shell will add to the explosive energy of the shrapnel (also KE). --Chris

(edited for ascii graphics)

[This message has been edited by Maastrictian (edited 08-05-2000).]<HR></BLOCKQUOTE>

Chris

Yes but mostly no. The argument is that the KE will add to the explosive energy.

I am maintaining that direct fire HE is being used against hardened targets. Bunkers, houses, Pillboxes of various construction, etc.

Lewis

[:USERNAME:]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Pillar:

It seems really simple to me.

The advantage of slow speed HE is that it will not dig into the target too much before exploding, thus a wider area of effect.

The advantages of speed include penetration (if it is desired), accuracy, and naturally time to target.

So it simply depends on what you want to hit and why you want to hit it.

PS -- Whats "Apropos" mean? Honestly.<HR></BLOCKQUOTE>

Pill

Yes and as I have said INDIRECT HE fire is great for your first example (troops in the open lets say)and DIRECT HE fire is great for your second example (hardened targets). Also I maintain that the KE gives an extra slam on the HE whammy.

Apropo means pertinant or close to that. Its an egghead word.

Lewis

PS You are dangerously close to agreeing with me.

[PzKpfw 1]

<BLOCKQUOTE>quote:</font><HR>Originally posted by :USERNAME::

You the hostess here directing traffic?

<HR></BLOCKQUOTE>

Nope, do you feel the traffic needs directing?.

<BLOCKQUOTE>quote:</font><HR>

First off, I am waiting for Norwood the alledged prof to clear up his "dot product" pontification. i think hes full of it.

<HR></BLOCKQUOTE>

Now thats better a bit crude but better.

<BLOCKQUOTE>quote:</font><HR>

What the hell are you rambling about? Are you mixing up philistines post with norwoods? <HR></BLOCKQUOTE>

I'd think that would be obvious from my last post Lewis, no need to go into it again here.

<BLOCKQUOTE>quote:</font><HR>

Now I see other people are contributing so get off the soapbox unless you can also.

<HR></BLOCKQUOTE>

Yes it is as I hoped it would.

Heh Lewis, you have never seen me get on a soapbox, and hopefully you never will, its not pretty.

I try to treat people with common courtesy, if someone disagrees with me I listen and let the discussion devolop if I'm wrong so be it, no personel attacks,etc.

Regards, John Waters

[Guest Pillar]

Agreed, the extra speed would add some to the "whammy"

However, the round getting burried into the ground would take away from the damage to the lucky sons of b*'s

I think that the point originally made was that it's better to have the round explode with shallow penetration when trying to kill with HE rather than get the extra energy from speed at the sacrifice of a buried round.

That would also seem to make sense.

So I think you both have some good points, but are only arguing different uses of the HE round.

What you should be arguing is not physics, but probability. What am I most likely going to use an HE shell for?

The answer to that question will yield the proper course of action.

- Pillar

PS -- AND CUT OUT THE SNIDE CRAP! ALL OF YOU! (Self Appointed Policeman Pillar)

[:USERNAME:]

LOL

Police, hostesses, what next?

See my infamous "skipping rounds" posts for how I feel about using HE against troops in the open..

Kennzahl fur sprengstoffart

Anyone can translate this german I found on the side of a german HE shell, yah?

Lewis

[Maastrictian]

Lewis wrote:

<BLOCKQUOTE>quote:</font><HR>

The arguement (or at least part of it) seems to be that the KE of the shell will add to the explosive energy of the shrapnel (also KE). --Chris

<HR></BLOCKQUOTE>

Yes but mostly no. The argument is that the KE will add to the explosive energy.

Isn't that what I just said? The KE of the shell will add to the explosive energy (also KE as the PE of the explosive is converted to KE in the shrapnel and adds to its KE. KE(due to muzzel velocity) + KE(due to explosive) = KE(of the shrapnel).) My arguement, that I demonstrate in my last post is that KE (due to muzzel velocity) is significantly < KE (due to explosive). This is because, as I show, Vs < Ve.

<BLOCKQUOTE>quote:</font><HR>

I am maintaining that direct fire HE is being used against hardened targets. Bunkers, houses, Pillboxes of various construction, etc.

<HR></BLOCKQUOTE>

Question: are you maintaining that 1. the *only* use of DF HE is hardened targets, 2. or that, in the hardend target case, the shell velocity is more important than the explosive (and for soft targets explosive is more important), 3. or that shell velocity is more important than explosive for both the hard and soft target case.

In responce to your point (above) I'll say that my arguement in my last post (reviewed above) that Vs is lower than Ve certainly applies here. Remember, that is Ve is 20 times greater (as I estimate in my last post) than Vs then the coresponding KE difference is 400 times. (because of the squared velocity). Note that this difference only applies to shrapnel that is thrown forward, shrapnel that is thrown to the sides will only have Vs factored in when we are considering the effect on the surface we are impacting on (the wall of the bunker). But, if any of the shrapnel is going to penetrate, it will not be the Vs only shrapnel blown to the sides by the explosive, but the Vs + Ve shrapnel blown towards the target. And (not to beat a dead horse) we know that Ve is much higher than Vs.

--Chris

[Deuce]

IMO there's not much to argue about here.

Let’s define three general cases where one might use HE direct fire.

1. Against infantry. This includes infantry in the open, in buildings, in the woods, in their underwear, etc.

2. Against lightly armored targets. Trucks, halftracks, carriage guns, etc.

3. Against pill boxes and bunkers, and anything else like #2 above, but better armored.

For case one it seems obvious that maximizing your HE payload at the cost of propellant payload pays dividends. Your not looking to actually HIT the target so the extra accuracy of a higher muzzle velocity is not as important as having lots of shrapnel whizzing around real fast, and the biggest factor in how fast your shrapnel is flying around is how much HE you have crammed in the shell. Assuming the shell detonates on impact (we'll ignore any sort of special fusing for now) each piece of shrapnel has a component of velocity imparted by the explosion (Ve) and a component imparted derived from the velocity of the (ex)shell (Vs), this component is always parallel to the path of the shell. So, basically Ve is what’s causing those bits to spread out (of course some of the bits will a Ve that is parallel to Vs, but most won’t) and Vs is driving them towards the ground, hillside, building… whatever you were aiming at. At this point it is clear that if Vs is zero the shrapnel spread is maximized because each bit can travel farther before striking the ground. Fortunately none of this really matter’s, because Ve is so much larger than Vs that the effect is highly minimized.

Case two is a similar to case one with the added complexity that you are actually shooting at a thing as opposed to an area. Let’s take the example of a tank firing at a gun emplacement. Higher muzzle velocity is a more advantageous here, but only because is makes aiming easier. The extra “smash” that higher speeds provide is not important, because a direct hit would likely disable the gun even if it where a dud and as pointed out in case one, should you miss, there is no benefit to higher shell velocities.

Accuracy is the most important in case three, because bunks and pillboxes are protected from near misses. However if the walls of a bunker are so thin that a high velocity HE round will penetrate them, then an even higher velocity (and thus more accurate) AP round will certainly due the trick as well. Since case 1 and 2 where more common than 3, and since AP can be substituted to some effect, it seems that HE shells, ought to be designed to maximize there lethality in case one and two, that is, higher payloads at the expense of speed.

Using the above thoughts it seems that the amount of HE in the shell has vastly more effect on it’s lethality than higher muzzle velocities for most targets (within reason of course, a 5mph bullet isn’t much good).

When thinking about the propellant to explosive ratio what must be decided is how fast must the shell travel to accurately place itself close enough to the target for its blast to be lethal.

[:USERNAME:]

Good points being brought up.

One of the things people dont normally appreciate about HE shells and wall thicknesses is the reasons behind it.

Many people know there is an extreme pressure behind the shell (trapped by bands around the shell) and of course this means the back of the shell has to be thick so as to not deform, etc. But the sides of the shell are a different matter. They need to be strong due to the incredible torque they are experiencing going down a rifled barrel. For a shell to get a spin, the bands dig into the rifling and rotate the shell as it proceeds up the barrel. Next time you see footage of an old rifled tank or arty weapon, notice that there is not just a backwards recoil but also a side twisting as the gun counter reacts to the rifling. The wall thickness on the shells have to handle this force primarily and THAT is the reason behind it. The front usually has the fuze assembly and has to be strong enough to last for the duration of the fuze time.

****, I just realized that there is not only a translational KE but also a ROTATIONAL!!!! Damn Im smart.

Lewis

[Deuce]

I hadn't though of that. I would guess that the rotational KE would be trivial compared to the linear KE and that imparted by the explosive, but I don't really know. Here are the equations for someone who knows what numbers to put in them.

Rotational KE around a fixed axis (axis p we'll call it)

Kp = .5 * Ip * Op^2

where Kp is the rotational KE around p. Ip is the moment of inertial around axis p and Op is the angular velocity around axis p (should be an omega instead of an O, but I don't have that key )

for those who care you might notice that this is the same as

KE=.5mv^2, but with angular kinematics terms substitued for the linear ones.

To find Ip for a piece of shrapnel at the edge of the shell you would use

Ip=(mass of the bit of shrapnel)*(the distance from the shrapnel to the axis of rotation)^2

I have no idea how fast a shell rotates so someone else will have to crunch this out.

[Deuce]

Just occured to me. Those equations won't be intirely accurate, because I'm sure there's some wobble in the shell's axis as it flys. I'm guessing there's not much though so it shouldn't make too much of a difference

[:USERNAME:]

If someone knows the turns per length for the rifling then its easy to figure out.

Admittly a small effect Im sure. Whats funny is that you read everywhere that the rotation on a HEAT shell has a great effect on penetration but its always stated that velocity doesnt matter! May have something to do with the way the penetrator needs to "form".

Lewis

[Deuce]

That’s interesting. Also, the faster the projectile rotates the less wobble you get as it travels to the target, thereby ensuring that the path of the penetrator is as close to parallel with the path of the shell as possible. Which would maximize the velocity of the penetrator.

[dalem]

Lewis-

No one in this thread ever implied that shell velocity doesn't add to the total energy at point of impact. We just tried to point out that the relative effect on the target is essentially trivial.

If I believe the quantum physics laddies (and I do), then there is a tremendously small yet finite chance that all of the particles of my body might suddenly appear on oh, say, Pluto. Yet the probability of that happening is so close to zero as to be zero. So I don't worry about it.

Likewise, there is an incredibly small yet finite probability that you might not drag a thread out by 50 posts by being an obfuscating spaz. Alas, most of us know that the probability of that happening is also so close to zero as to be zero.

Just because you read some equations somewhere doesn't mean you know how to use them - you must think of proper scale before you fire up those brain cells of yours.

-dale

[Guest Germanboy]

<BLOCKQUOTE>quote:</font><HR>Originally posted by :USERNAME::

Kennzahl fur sprengstoffart

Anyone can translate this german I found on the side of a german HE shell, yah?

<HR></BLOCKQUOTE>

Inventory number for type of HE.

Kenn zahl für Art Sprengstoff

------------------

Andreas

[:USERNAME:]

<BLOCKQUOTE>quote:</font><HR>Originally posted by dalem:

Lewis-

No one in this thread ever implied that shell velocity doesn't add to the total energy at point of impact. We just tried to point out that the relative effect on the target is essentially trivial.

If I believe the quantum physics laddies (and I do), then there is a tremendously small yet finite chance that all of the particles of my body might suddenly appear on oh, say, Pluto. Yet the probability of that happening is so close to zero as to be zero. So I don't worry about it.

Likewise, there is an incredibly small yet finite probability that you might not drag a thread out by 50 posts by being an obfuscating spaz. Alas, most of us know that the probability of that happening is also so close to zero as to be zero.

Just because you read some equations somewhere doesn't mean you know how to use them - you must think of proper scale before you fire up those brain cells of yours.

-dale<HR></BLOCKQUOTE>

Dale

Actually your first post went on about your liver and shrapnel or something like that. I am not talking about shrapnel but the blast effect. You were confused then but are just getting wierd now.

Heres an experiment for you Dale. Drop a 15 pound weight from the ceiling on your head. Report back to us with any quantum or classical physics the "laddies" in your head tell you.

Lewis

PS "Oh well, I'm probably not adding anything of value, so bye bye for now. -Dalem"

Still true.

[:USERNAME:]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Deuce:

That’s interesting. Also, the faster the projectile rotates the less wobble you get as it travels to the target, thereby ensuring that the path of the penetrator is as close to parallel with the path of the shell as possible. Which would maximize the velocity of the penetrator. <HR></BLOCKQUOTE>

A ballistic problem with the hollow charge shell is the cavity up front. This leads to a very unstable flight as you point out. Most of these rifled fired HEAT shells werent very good at hitting targets beyond 500 meters. And the spinning degraded the penetration also.

Lewis

[:USERNAME:]

Heres a list of German weapons firing HE versus 0 degrees (vertical) ARMOR and the effects of range.

75mmL70 "Panther" 69mm@100m 45mm@2000m Blast 34

105mm "StuH42" 62mm@100m 47mm@2000m Blast 77

50mm "Puma" 30mm@100m 19mm@2000m Blast 14

88L71 Tiger II" 93mm@100m 65mm@2000m Blast 50

I am attempting here to discredit peoples "poopooing" that velocitys have little effect on AP or Blast effects of HE. As it is evident, BTS has wisely modeled the effects of HE's different velocities (range) on ARMOR penetration. Notice how the obviously longer range weaker penetrations can only be accounted for by the "scrubbing" of velocity to the atmosphere. Even with a small HE charge (as in the 50mm weapon), a great deal of the lost penetration must come from the LACK of VELOCITY. I would not call the contribution to armor penetration minimal in the above cases. Some are increased up to 50 percent and there is still a component FROM velocity at 2000m!!!!!!!!!!!!!!!!!!!!!! (wow long burst there)

Now these same HE shells are not going to lose this great deal of energy when fired at anything else. this goes against ANY scientific persons appreciation of the conservation of energy. If the supposed college proffessor will refute this, I would be happy to discuss it with perhaps proffs that have taught me or maybe he would like to include his fellow proffessors?

Perhaps Charles could illuminate us on the 'Blast' number. Is it fixed, range (velocity) dependant, modified for critical hits, etc?

So I still stand by the following statements:

Velocity adds an appreciable effect to both the AP and Blast effects of HE shells.

Velocity adds to the accuracy of HE shells as any other shell

Velocity decreases flight time and allows qucker adjustment of fire.

Hardened targets are best attacked by blast effects than 'shrapnel' effect.

Hardened targets mean bunkers, buildings, pillboxes, trenches, caves, etc.

Direct fire Blast effects require hits to be most effective.

If we take the supposed assumption of "that the more the HE the better", then we can logically extend this so that we choose a mortar as the main weapon of our direct fire HE weapon (since as we reduce the velocity, the barrel will have to get a greater and greater angle to engage a target!). Mortars can pack more HE in a shell of similar size than a rifled weapon (one of the main reasons IS the rifling -see the HESH posts). Something like 10 percent for rifled shells and 30 percent for mortars...? Why didnt the british put 3 inch mortars in their close support tanks? Mr Heidman maintains that "you probably arent going to hit the target anyway". So just use mortars then!

The germans were the first to really get the infantry support role of vehicles right and went to alot of trouble to maintain a seperate arm (sturmartillerie) and school (Juterburg) that specialized in sturmgeshuetz. Emphasis WAS placed on keeping this an elite arm and even towards the end of the war had a majority of volunteers for the gunners. Accuracy was especially emphasised and this was an elite form of artilleryman. The volunteers had a great appreciation of high explosive before they even got there. Whittman BTW served in stugs before he was Mr Tiger Tank. He used his stug split-lens optics even with his tigers. He knew his real enemy on the eastern front was a dug in 76.2mm ATG.

Direct fire infantry support HINGES on stealth (since you are operating at fairly close quarters to the enemy), QUICKLY engaging targets and HITTING them with minimal rounds and changing positions. Weapons like the soviet JSU122s give me the willys. Big HE with a kicking velocity. CM2 look out.

Lewis

[Guest Germanboy]

You are most welcome Lewis, it is good to see that common courtesy is still alive and kicking in your neck of the woods.

------------------

Andreas

[:USERNAME:]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Germanboy:

You are most welcome Lewis, it is good to see that common courtesy is still alive and kicking in your neck of the woods.

<HR></BLOCKQUOTE>

A thousand pardons..

I missed your answer in my flurry of responses. I see you broke up the words (kennzahl to kenn zahl?)and left a little off the last.

How about the following:

Ort, Monat,, Jahr des aufschraubens des zunders und kennbuchstabbe des dafur verantworlichen

(month day year? whats the rest?)

Again my apologys

Lewis

Lewis

[Guest Germanboy]

<BLOCKQUOTE>quote:</font><HR>Originally posted by :USERNAME::

A thousand pardons..

I missed your answer in my flurry of responses. I see you broke up the words (kennzahl to kenn zahl?)and left a little off the last.

How about the following:

Ort, Monat,, Jahr des aufschraubens des zunders und kennbuchstabbe des dafur verantworlichen

(month day year? whats the rest?)

Again my apologys

Lewis

Lewis<HR></BLOCKQUOTE>

Kennzahl was broken up by me b/c English broke it up into inventory and number, not being amenable to long words.

The other stuff:

Place, month, year of unscrewing (opening) of the fuse, and personal (signature) letter of the responsible person

All quality control stuff.

------------------

Andreas

[:USERNAME:]

I made a mistake. That was an German AP round.

Thanks anyway for the translation.

Lewis