M7 Priest as Artillery?

[JasonC]

Other Means - 14 kilometers is typical for the standard div arty pieces. Maybe only 12 km for some of the howitzers. Guns meant for long range counterbattery (gun rather than howitzer, e.g. German 170 or US 4.5 or Russian 122 gun) would be more like 18 to 20 km. Rockets on the other hand are short range weapons by comparison, with 5-6 km maximum range. Medium mortars (120mm, 4.2 inch) are similar - about 5 km. Light mortars more like 2-3 km, varying with the weight of the round used.

[JonS]

Originally posted by Other Means:

Also, I never knew about crater analysis. I'd assumed some kind of spread analysis but that the craters were more or less dominated by the HE spread. Live and learn.

It's pretty rough, but you can determine the calibre and the approx bearing the rounds arrived on. I think you can also take an educated stab at the range, but I expect there'd be a huge error associated with it.

As an example of usage: Once you get a couple of crater analysis reports it's possible to do back bearing 'resections' to get a rough location (with a fairly large triangle of error), and from there you can do a map recce inside the triangle, or task some air recce, etc, to get a better location.

ISTR that there are some current US Army pams online dealing with crater analysis if you're more than passingly interested

http://www.globalsecurity.org/military/library/policy/army/fm/6-121/fm612_9.htm

http://www.globalsecurity.org/military/library/policy/army/fm/7-90/Appd.htm

http://tinyurl.com/yhr2g5 (html of a powerpoint presn)

Lot's of stuff about British CB in WWII here.

[ December 15, 2006, 04:53 PM: Message edited by: JonS ]

[John Kettler]

It was shortly after learning about crater resection that I found in Dad's KOREA: The Land of the Frozen Calm (a Stars & Stripes cartoon anthology) a topical cartoon in which we see a hurricane of shell bursts outside a cave mouth and two guys within, one on a radio handset. The speech balloon? "They want us to go outside and ascertain the direction from which the fire is coming."

I last read the manual on crater resection in the 1980s, but as I recall, crater shape alone generally allowed rapid determination of whether it was mortar fire or standard tube artillery. Mortar fire, because it arrives via a high looping trajectory, tends to arrive near vertically, creating a basically round crater. Tube artillery, fired on a lower trajectory, by contrast creates a crater which is markedly exaggerated along its axis of fire, effectively oval. Once the size of the weapon is known, also obtainable by analyzing fragments recovered from the crater, it is indeed possible to get at least a first order range approximation, simply by seeing how ovoid the crater is compared to known prior cases. The more ovoid it is, the farther away the gun that fired it.

Regards,

John Kettler

[Other Means]

Jason, Jon, John, cheers for the answers - very educational.

So if a standard max range for your 25pdr's/155's is 14km, and on the front foot you have them 1/3 max range forward, that means we start at 4km shoots.

What minimum safe distance to troops does that give us? Does it increase the further away from the guns? Does the FO have a chart saying where the guns are and therefore how close he can call fire in?

How accurate over that range was the standard, I'm trying to ask.

If an FO is calling in ranging fire he's doing it with one gun - yes? So when he calls FFE, there must be quite a distribution, with WWII technology, around that point. Even for a single gun I'd have thought we'd get (finger in the air) ~25m radius deviation.

Is the spread we see in CM reasonable? Within a magnitude?

Thanks guys.

[JonS]

Hi OM,

that's a fairly complex series of questions, which will take a bit of time to answer. Unfortunately, I don't have any right now, but will try to get back to you later.

In the meantime, Nigel Evans' site is very good on all this stuff, although it has a very strong - basically total - focus on the RA. The US and German artillery was broadly similar, but there were some significant differences too - especially in command & control and FOO techniques & procedures.

Start page for his site is here. Look especially at the Technical Fire Control during WWII, Errors and Mistakes, and the Ballistics and Data pages.

Jon

[Other Means]

I appreciate the effort Jon.

I've looked at Nigel Evans' site many times, I'm always amazed that it's not on a proper government website somewhere.

Looking quickly now at the Errors and Mistakes section I can see that I've never really thought about muzzle wear, propellant temperature, batch differences etc. I'm guessing this would preclude some kind of standard chart for minimum safe distance.

Or at least, one that would basically act as in CM, where you can bring the shells in right over the heads of your infantry?

[JasonC]

Other Means - the typical tolerance for fire missions was 400 yards from friendlies.

Sometimes attacking infantry would push and follow a barrage more closely than that - a practice called "leaning on the barrage" - but did so expecting it would mean some wounded from shrapnel on the shorter rounds. It was just sometimes judged preferable to giving the enemy more time between shells passing over and infantry arriving, because MGs would do more damage that way than the shrapnel did.

Another case when closer fire was sometimes used was "final protective fire", which would be called right in front of the defenders and occasionally right on top of them. This was only done when the defenders have overhead cover, and the idea was for them all to know it was about to happen and get deep in their holes. Then the arty sprayed fragments over the whole area, intending thereby to "nuke" enemy infantry overrunning the position.

Both were desparation measures. For ordinary use, a barrage was called 400m ahead of friendlies, as explained at the outset.

The error does not appreciably grow with the range of the shoot, in range. In deflection (side to side) it does, roughly linearly. But since few shoots were in the bottom third of the range and front line ones weren't typically over 3/4 or so, the spread between nearest and longest shoot is not that large.

Deflection spread is dominated by the sheaf anyway. A typical shoot is parallel sheaf, meaning all guns fire on the same compass heading. That means the rounds will tend to fall in the same spread pattern as the guns in the firing battery or battalion. Each then "smeared out" by its own dispersion, of course. Since the guns were spaced 50 to 100m apart themselves, they covered a fairly wide area, and the dispersion tended to fill in the gaps.

What you see in CM for a standard order, on the other hand, is more like the dispersion of a single gun, or of a "closed sheaf". That means all the guns are firing on converging angles, the rightmost about 1 mil left, the leftmost 1 mil right, the next in half a mil, etc. That is the way to shoot at a *point* target, rather than an area target. But it was not the standard thing.

In part because - other big abstraction in CM - the actual aim point for all these guns is itself smeared out by the spotting round process. You can't tell from 1-3 spotting rounds exactly where the gun that fired is pointing. I mean, they come down some random place *around* where it is pointing, but not smack there.

The biggest single inaccuracy in CM is that the center of your fire mission shell oval is always exactly where you ask it to be, for an "accurate" mission anyway. In reality, the aim point itself would drift 50-100m, and then you'd see the smeared shell fall pattern around *that* point, not the one you wanted.

And no, you can't make up for this by just firing several spotting rounds and correcting each. Once you are within about twice the dispersion the gun itself adds, additional adjustments will smear out the fire pattern more, not tighten it up. This happens because adjusts are effectively "positive feedback" to runs of randoms that break the wrong way.

Same thing happens in rifle marksmenship, it instead of aiming center of mass consistently, you try to compensate for where the last round went - you just walk your aim point around wider than it needed to be walked, and add that dispersion to the original one coming from the gun. It is a mistake to try to get a gun to behave like a laser - once you are within the dispersion, you should call it good enough and just shoot.

In the case of standard artillery barrages, that was formalized by FOs using 100m increments for adjusts. Occasionally they went down to 50m, but thinking that using 50m adjusts will get you 50m accuracy is an example of the above mistake, and like as not, it will instead reduce it.

Now, clearly when you are firing a pattern whose *centerpoint* can easily be off 100m, since you want the *intended* aim point not just the actual aim point to be within the barrage, you want to fire a pattern that is several hundred meters wide. If you fire a pattern 400x400, and the center is 100m away from where you wanted, who cares? The whole middle portion of the barrage still covers the intended aim point. In practice, battalion shoots did aim at areas that large. Single batteries, more like 200x200. Think bludgeon not scalpel.

We don't see those often in CM because people instead try to exploit the perfectly located barrage centerpoint for "scalpel" effects. And then the game designers see a need to make reactive artillery hyperexpensive, lest it decide all fights. And then hyperexpensive modules encourage scalpel use because shells are too valuable to "waste" on wide targeting. And to avoid tiny small shoots by a few shells aimed just so, defenders then play dodgeball with each flight.

Which is silly, didn't happen. Try dodging 3 FOs aimed at different points about 100m apart each using "target wide", and walking said aim point every 2 minutes, stretching the barrage out in the process. That is much more like what a typical WW II field artillery pattern looked like. And its target wasn't a platoon because the FO saw them 30 seconds ago, is was a battalion that had to have some subunits in that general area.

The required efficiency of big shells in CM is approximately, a medium module has to smash a platoon with 40-60 shells. Which means roughly that 1-2 shells are expected to neutralize a man on the targeted side.

In the real deal shells were not remotely that scarce. If 10 medium or larger shells got 1 man, the enemy would run out of men even if the rest of your army sat the war out watching the fireworks.

In practice it sometimes got 1 in 10 to 1 in 20, and anything like the lower figure would make it operationally very effective, alone. Regardless of what else was going on. By which I mean, a force that gives the enemy artillery such shots regularly, will bleed to death in a matter of weeks, leaving not enough left to hold the line.

When it got 1 in 25 to 1 in 50, it supplemented other arms but would not be decisive on its own. Drives defenders deep in their holes or cellars etc.

In CM terms, a battalion level "3 target wide and walking" shoot, only needed to take out a few squads to be worth it, and if it gets a full platoon it is a big success. Any occasion with a dense enemy infantry target not in deep cover, suffices for that. So there was no need to reach for scalpel level control, which wasn't really available anyway.

And since the arty wasn't aiming for that, dodging was pretty pointless and impossible. On a heavy enough barrage, you just gave up the mission completely and went as deep as possible. The maneuver war was on "pause".

[JonS]

Well, I don't really have much to add to that then One simple enhancement to CM (incl CMSF) would be to make the minimum adjustment of artillery 50m. Which is about the minimum adjustment that FOOs bother with in the kinds of missions you see in CM. That would - in large part - avoid the 'scalpel' effect that Jason talks about, encourage the use of target wide, etc. It'd probably also see artillery disappear from QBs, since that lack of control probably wouldn't suit most QBers.

To put some specific numbers around what Jason was talking about, when aiming a gun the error is broken into PEr and PEd, which is the abbrevs for Probable Error (range) and Probable Error (deflection). FOs don't typically bother with PEd, since working from memory it is on the order of 6-10m at typical ranges. PEr, on the other hand, can be quite significant. The following table is for the British L119 Light Gun firing US M1 ammo (which is more-or less what US 105mm divarty used in WWII) at Low Angle:

When preping up for a mission, the FO consults the above table, starting with range from guns to target. Then he selects the minimum charge that gives at least 1000m overlap. Then he looks to see what the PEr and Time Of Flight is. So, eg, guns-target is 7000m, charge selected is Chg6, PEr is 15m and TOF is 25 seconds. When adjusting (one round from one gun) the rounds are moved around by the FO calling adjustments until they are within 2 x PEr long or short of the target, so in our example that's 30m long or 30m short. As soon as you get a round within those limits, it is considered 'on' and you go to FFE.

For comparison, here is the High Angle table. Notice the increase in TOF, and that each charge has a specific minimum and maximum range, unlike the LA table where each charge can in principle achieve any range up to its maximum. In theory, the PEr is the same for HA or LA, but in practice, because the round is floating around up in the aether for so long - and thus subject to wind and changes in air density for far longer - it tends to be wildly inaccurate. Also, HA rounds are much easier for CB radars to detect.

Now, in terms of getting rounds close to friendlies, the following table has the lethal, safe, and planning distances for various weapon systems. 'Lethal' is considered fatal to anyone standing up unprotected, 'Safe' is the distance at which you should be ok if out in the open, while 'Planning' is the distance FOs are expected to work to. Any closer than 'Safe' requires the explicit consent of the supported-arms commander.

Distances are in metres, and are measured from the point of aim, or centre-of-mass of an FFE.

Except ... it's not quite as simple as just using the safe distance. If the guns are firing from directly behind the friendly forces (or directly toward ... it can happen) the 'Safe' distance is increased by 4 x PEr. So, continuing our example, the SD for L119s is 250m, and PEr was 15, so the safe distance when firing directly overhead is 310m, which is still quite a lot of ground for the infantry to cover in an assault, and way way longer than anything you see in CM.

Oh. Those tables are above are for current equipment and current doctrine, but you'll hopefully get the broad idea from that about how it was done in WWII.

Regards

Jon

[ December 16, 2006, 11:22 PM: Message edited by: JonS ]

[Other Means]

I see, mainly. The dispersion within (2 x PEr) is considered as close as you're going to get, so then you go FFE, and there are various tables that can account for what PEr is, with PEd dispensed with as it's smaller than PEr.

So there is a table to account for the closest safe range, with the ability to call fire in on top of your position when things are dire. What a choice to have to make.

There's one issue I'm a bit confused with, are these statements contradictory?:

JasonC

The error does not appreciably grow with the range of the shoot, in range. In deflection (side to side) it does, roughly linearly. But since few shoots were in the bottom third of the range and front line ones weren't typically over 3/4 or so, the spread between nearest and longest shoot is not that large.

I know Jason is saying the error doesn't really grow but

JonS

To put some specific numbers around what Jason was talking about, when aiming a gun the error is broken into PEr and PEd, which is the abbrevs for Probable Error (range) and Probable Error (deflection). FOs don't typically bother with PEd, since working from memory it is on the order of 6-10m at typical ranges. PEr, on the other hand, can be quite significant. The following table is for the British L119 Light Gun firing US M1 ammo (which is more-or less what US 105mm divarty used in WWII) at Low Angle:

Jon seems to be saying that it does, and here's a table to plan by? What have I got wrong here?

Anyway, I think I'm getting a much better grasp of what we could have expected to see, and I'm also kind of convinced BFC gave us a reasonable compromise with the intended size of the games.

Thanks gents.

[JonS]

Originally posted by Other Means:

I see, mainly. The dispersion within (2 x PEr) is considered as close as you're going to get, so then you go FFE, and there are various tables that can account for what PEr is, with PEd dispensed with as it's smaller than PEr.

PEr is essentially random error that cannot be accounted for otherwise. Barrel wear and muzzle velociy is accounted for as is weather (sort of ... it is accounted for, but it also changes between the time it's recorded and the time it's applied), variations between ammo and charge lots should be accounted for, charge temp should be accounted for, but there are loads of other things that aren't. However, round to round, they are basically the same, and they all get lumped under PEr.

So there is a table to account for the closest safe range, with the ability to call fire in on top of your position when things are dire. What a choice to have to make.

Wait .. I reproduced that table above? For 105mm the SD is 250m, which might have 4 x PEr added depending on the line of flight. That is as close as the FO is allowed to bring them in. Rounds can of course be brought in closer, but requires the explicit consent of the supported-arms commander.

There's one issue I'm a bit confused with, are these statements contradictory?:

[snip]

Not sure. Both PEr and PEd increase with range, but PEd does so at a much slower rate. One figure I saw for M1 ammo while rummaging around for PEd was 1-mil, which means that at 1,000m range PEd is 1m, at 5,000m its 5m, and at 10,000m its 10m.

PEr is as above. As you can see it increases with range too, and is substantially larger than PEd.

[Other Means]

Excuse me while I digest this. Thanks for the info.

[C'Rogers]

To go back to the original concept of the Priest and changing it on map to indirect fire, while certainly realistic, seems to be out of game scope as a company level game. It seems like it could be more used in a gamey concept then realistic. While it has been shown in this thread the rate at which Priests could change between fire modes were they sent into battle with that intention?

What little I know of the issue in comparison to others here a Priests wouldn't be dispatched to the frontline under the instruction that to use either direct fire or indirect fire given the circumstance. It seems that there role would be designated ahead of time and only in an emergency would a switch be done.

[Harry Yeide]

Originally posted by C'Rogers:

To go back to the original concept of the Priest and changing it on map to indirect fire, while certainly realistic, seems to be out of game scope as a company level game. It seems like it could be more used in a gamey concept then realistic. While it has been shown in this thread the rate at which Priests could change between fire modes were they sent into battle with that intention?

What little I know of the issue in comparison to others here a Priests wouldn't be dispatched to the frontline under the instruction that to use either direct fire or indirect fire given the circumstance. It seems that there role would be designated ahead of time and only in an emergency would a switch be done.

Not necessarily gamey, but unusual. M7s used as assault guns (units beside the 117th Cavalry Reconnaissance Squadron that did so included the 1st Armored Division and 751st Tank Battalion in Italy) would fire as circumstances required.

[John Kettler]

And the same was true of the halftrack mounting the French 75mm gun and the M-8 HMC, both of which I've repeatedly seen described as assault guns. To me, such an appellation automatically connotes a direct fire role using HE.

Regards,

John Kettler

[JasonC]

Priests were meant to be used indirect, not as assault guns, and got the direct role only in defense situations, or perhaps occasionally block or bunker clearing I suppose. But the preferred weapon for the latter tasks was the Sherman 105.

The Sherman 105 and the M8HC were both designated "assault guns". Both were actually used for indirect fire at well, however. The M8HMCs, at least in the cavalry, mostly fired indirect, since they were the only organic fire support of the cavalry squadron.

The task of shooting up MG nest and the like could be done by armored cars, or the Stuarts of the light tank company. Occasionally though, e.g. in moving offensive missions, the HMCs went along with the latter in the attacking columns.

The Sherman 105s occasionally fired indirect as a battery - it was common in Italy e.g., in hill fighting. But their most common use was as an actual assault gun, since the ADs abundant Priests could do most of the indirect shoots.

Another place there were M8HMCs, where they may have been used more often in a direct fire role, was in each armored infantry battalion (3 each). They were parallel in organizational terms to the battalion's 81mm mortar carriers, but in practice an AIB might have had more call for busting MG nests etc.