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"Effect of indirect artillery fire" Topic


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2,104 hits since 31 Jul 2019
©1994-2020 Bill Armintrout
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Mobius09 Aug 2019 8:04 a.m. PST

You mean from a direct fire flat trajectory round than arced from a mortar or howitzer …
No, that is a given. I mean from a shell fired from say 9 kilometers impacting at 30° compared to one impacting at 60°. This is a hectare comparison. If the beaten zone is smaller for one than the other the percentage goes up.

Legion 409 Aug 2019 1:39 p.m. PST

I see … but a bit out of my league. I knew how to call-in mortars, FA, CAS and even Naval Fire Support. But the math/science behind a lot of it … is beyond me.

Blutarski09 Aug 2019 5:03 p.m. PST

Hi Legion 4,
The graphical fragment distribution patterns of various ammunition types given in TM9-1907 "Ballistic Data Performance of Ammunition" (1948) and the statistical analyses of number and size of fragments created by the explosion of any such projectile were very helpful to me in clarifying the different personnel casualty effects produced by mortar fire versus low angle gunfire.

Simplistic story – The explosion of any high explosive round generates a 360deg disk of fragments projected at right angles to its longitudinal axis. While the diameter of this fragmentation disk can be fairly substantial, its thickness is quite modest (10ft?). According to the diagram, you could be standing 20ft from the landing point of a 105mm round and stand a good chance of not being hit by any fragments. For a flat trajectory gun, jam a Frisbee edge into the ground vertically on edge (so it looks like a "Star Gate" in SG1). The flat of the Frisbee will be perpendicular to the line of fire and it suggests that the large majority of the fragment pattern is wasted into the air.

For a mortar, lay the Frisbee flat on the ground to understand the relationship of the fragment pattern to the surface of the ground if the round struck with a 90deg angle of fall. Of course, no shell falls at 90deg; In the real world, a mortar round's angle of fall is apparently ~60deg. In that case, the casualty radius on the forward 180deg arc of the shell strike will only extend about 15-20ft, since the fragments will tend to rise a bit. But the fragmentation effect on the rear 150deg or so will extend out fan-wise to about 40ft.

Plus, caliber for caliber, the mortar shell tends to create more casualty-inducing (as opposed to lethal) fragments.

Summary, the mortar is ideal for engaging enemy NOT dug in or in otherwise good hard cover. Artillery gets the call when the enemy is dug in.

No idea if I just bored you stiff with a lot of stuff you already know, but I got the impression from your last post that you might be unclear on the mechanics in play. If you know all this already, my apologies ….. ;-)

B

badger2209 Aug 2019 6:48 p.m. PST

I am on the other side from Legion4, 4 years as a gunbunny and 17 in the FDC. I have sent time mostly on 155mm, but a few years in 105mm. A few random comments about things above.

On one of our ranges we used to have some Pershings as targets. I hve seen a turret hit spin the turret a complete rotation. It did not seem to break the armor, but I bet that would suck to be in the turret when that happened.

ow long does it take you to drop to the ground? That is how long you have to inflict maximum damage on target. 155 does a much larger initial bang that 105. So by the time that quick second round gets there, most infantry is already as low as they can get.Dont worry about anybody still standing, they are way to stupid to be dangerous.

being under indirect fire sucks, mortars, light or medium artillery all suck. That said big bangs always seemed scarier, although I have not been shelled enough times to give you a really good comparison.

As it was explained to me in school, just as mortars have thinner walls, larger shells as a percentage of mass can carry more explosive than smaller ones.

During an actual battle, as opposed to a bombardment, we are more about disrupting the enemy than trying to wipe them out. We have fancy words for that now, but the old guys did the same things without the words. A dead guy is seriously disrupted, so that is a good result, but if we can make a MG crew duck that is almost as good, it just doesn't last s long. There is also recovery time. How long after you duck do you stick you head back up? I dot have any numbers for that, but again for me and everybody I have talked to about it, big booms are scarier.

Hope somebody finds this interesting. I found my job fascinating, hated when I had to retire.

UshCha10 Aug 2019 2:00 a.m. PST

Butarski and badger22, Thank you excellent insights.

Now we have the experts. If I read the manuals available to us the none serving folk. They take the shell the definition of the target and effect required and for each target type and shell size it gives a figure of area. How many shells to fire is then the area of the target divided by the "magic" number. Obviously the "magic" number goes down as the target gets harder, so the number of shells required goes up. Is this still roughly how it goes now? The manuals mutter darkly about addition data on the magic number (I DO NOT WANT THAT DATA THAT MAY BE KEEPING FOLK ALIVE. I just want to know if we have basically got it about right. Why because we have a VERY crude system that allows us to relate ammo usage to what it can do. Something other rules avoid high cost in plausibility.

Legion 410 Aug 2019 10:13 a.m. PST

Blutarski thumbs up

badger22 thumbs up

Like I said … I knew how to call-in mortars, FA, CAS and even Naval Fire Support. But the math/science behind a lot of it … is beyond me.

You call for fire on your radio … either you get it or you don't … frown

I'm a prime example of a "dumb" Grunt and product of our US Education system … evil grin

badger2210 Aug 2019 5:18 p.m. PST

UshCha what you suggest makes sense, but it isnt what we really do. Bn commanders or higher decide on general attack criteria, that gets sent down to BN FDC and away we go. The thing is, getting rounds on target before it moves away, or shoots up some grunts is way more important than some specific level of damage.

So what that means is that we already know what to shoot at something. one guy on a bicycle, grunt can kill that. Platoon of something, tankers can kill that. company of something on the move, BN 3 rounds.

Artillery simply is not appropriate in small sized actions. Every time you fire you expose yourself t possible counter battery. so you dont shoot unless it is worth it.

Artillery can be totally devastating or total worthless. and the difference can only a few seconds in the time it takes to get rounds on target.

Legion 411 Aug 2019 6:20 a.m. PST

Again badger22 +1 thumbs up On your entire post !


but it isnt what we really do.
Again what Vets really know about what happens vs. otherwise … Understandably in any light if you are only a gamer, read some FMs, etc.,.


I posted this here earlier – "As again in this case size does matter/bigger is better." …

I think what badger22 posted is a better way of saying it :

155 does a much larger initial bang that 105. So by the time that quick second round gets there, most infantry is already as low as they can get. Dont worry about anybody still standing, they are way to stupid to be dangerous.
thumbs up

And again from a Grunt's POV, we want to call in everything we can get, with all that is available. We don't really care if an FA shell is better/different in effectiveness than a mortar on certain targets. We want to attrite, suppress, destroy, maim, kill, etc., what is the immediate threat. Yeah a 155 maybe be better at "engaging" certain target types, etc. But if all you got is 4.2 instead of 155 … we'll take it ! And if both are available … we'll take both !

Blutarski11 Aug 2019 12:03 p.m. PST

One interesting point I recall reading about artillery fire effect is that, in terms of engaging a target of erect (no jokes, please) infantry, the effect of the first salvo to land will be about 3x greater versus anyone caught in its casualty pattern than following salvoes.

Reasoning – Anyone in the immediate vicinity of falling artillery will immediately go prone and doing so will reduce the soldier's vulnerability by a factor of 3.

….. which is arguably proof of the superior <<destructive>> value of a TOT mission fired by, say, six batteries compared to a conventional fire mission involving a single battery firing six salvoes over a period of time.

B

badger2211 Aug 2019 2:01 p.m. PST

Blutarski I think the effect is even greater than that, but your basic point is totally correct.

And, are you old enough to have played SPIs game Sniper? My favorite line of rules "if an erect man exposes himself in an aperture". Makes you wonder who was proof reading.

Legion 411 Aug 2019 2:08 p.m. PST

Yes … it's the "Surprise" factor … like an ambush. If it is done right … the "targets are serviced" before they know it.

Plus with incoming … Grunts will go prone and/or scatter looking for cover and/or just get out of the kill zone!

We did Immediate Action drills [all infantry does]. While Patrolling when incoming starts to hit. The leader calls out a location [far]away from the kill zone/blast radius using the "Clock System". E.g., "3 o'clock, 200 meters !" … But as always Terrain and Situation dictates everything. And there are few guarantees in war, AFAIK, I guess …

Even in an FM I have(d) showing the effectiveness of HE fires on troops, IIRC standing, kneeling, prone and entrenched …

the effect of the first salvo to land will be about 3x greater versus anyone caught in its casualty pattern than following salvoes.

When I was in a Separate Mech Hvy Bde. In about '87(?), our organic 155 SPFA(M109s) Bn reorganized from 4 Gun Plts of 6 tubes to 3 Plts of 8 tubes. I'm pretty sure that TO&E reorganization was generally Army wide.

Also in @ '84-'85, Mech Inf Bns did a reorganization too. But that is another topic for another time.

Wolfhag11 Aug 2019 6:49 p.m. PST

Blutarski,
Here what I think is a good estimate of causality profile:
link

Lastly, it's useful to note how vulnerability changes with posture because it suggests the relative amounts of fire needed in different circumstances. The following estimates the relative risks of becoming a casualty to ground-burst shells on ‘average' ground:

Standing 1

Lying 1/3

Firing from open fire trenches 1/15 – 1/50

Crouching in open fire trenches 1/25 – 1/100

Wolfhag

Legion 411 Aug 2019 7:28 p.m. PST

Good stats Wolf ! That sounds something like I was talking about in the old FM I referenced.

Legion 412 Aug 2019 6:14 a.m. PST

And, are you old enough to have played SPIs game Sniper?
Yes … old fart Great game ! I still think I have around here somewhere !


As badger22 said,

anybody still standing, they are way to stupid to be dangerous.
laugh evil grin

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