"Indirect Fire Artillery Classifications and 25 Pdr" Topic

That's probably about right given your level if granularity. How are you handling RoF. The 25 lbr was noted for its high RoF compared to similarly employed guns.

Weight of HE content rather than calibre might be a better classification?

Everything you wanted to know about the 25 pounder and more:
nigelef.tripod.com/maindoc.htm

Wolfhag

The US Army used them in Tunisia and after the Battle of the Bulge when there were ammo shortages for US 105mm howitzers. So if it's a good enough alternative for the US Army, then it should be good enough for you.

Mike Bunkermeister Creek
Bunker Talk blog

Tim-

I'd say that the better RoF would compensate for the reduced throw weight, so you're good to go.

For goodness' sake, Tim, pay attention.

Without bothering (because I have a bottle of an indifferent French red in the bag and a large glass of Muscat de Beaumes de Venise on top of it) to follow your link, I imagine that you have reference to the bizarre Canadian gunner norms which use 105mm equivalents, but whose 105mm-equivalent factors for other calibres bear a striking resemblance to those for 25-pdr equivalents taken from WW2 21AG OR reports (notably the "Bombardment of Wesel" report).

E-mail me your e-mail address, using juliet delta salt at golf oscar tango adsl.co.uk, where NATO phonetic letters are letters and the others are as is, and 'at' means @, and I shall cheerfully bombard you with a metric buttload of drivel in the form of my artillery snippets collection and a monograph entitled "factors affecting fragmentation fire". Normally I would wock them into a forum posting, but these are really quite large.

In return, I shall expect you to give me references to any open source numerical data on indirect HE effectiveness I have not yet found.

All the best,

John.

Ah, now I realise through the drunken haze that you did not, in fact, post a link.

But you were aware that Canadian gunners have been guilty of publishing norms that equivalate 25-pdr with 105mm on a shell-for-shell basis, no?

Which I think is crazy madness, because…

Oh, e-mail me for the gubbins. And the same for anyone else who cares to.

All the best,

John.

Is this for guns, or guns and mortars?

I'd count 4.2", 10.5cm and 120mm mortars as equivalent to 155mm guns, 8cm/81mm/82mm as equal to 105mm guns, and 60mm mortars equal to 75mm guns.

Reread your OP
try this
Very light Artillery, 70mm to 85mm
Light Artillery, 86mm to 101mm
Medium Artillery, 102mm to 120mm
Heavy Artillery, 122mm +

You are essentially looking at the differebce between 25lbs of bang and 30 lbs of bang………..

Soviet Field artillery 122 and 152 mm shells are both heavy – or rather heavy and very heavy
The self propelled version are classed as artillery but not used as such – they were used mainly for close e range inf support – ISU – 152 or longer range AT support ISU – 122

John have you gotten the norms from FM-100-2-1

chapter 9 – 22 page

link

PDF link

great info in FM-2-2.pdf and FM100-2-3

Lord Ghee

Going from the data at link I'd propose the following bands, each approx 50% better than the previous one in terms of effect:
60-84mm
85-95mm
100-114mm
120-135mm
140-170mm
180-220mm
230mm+

Of course the last two are for heavy and super heavy artillery so that would leave you with 5 bands for your game.

For targets in the open the size of the shell would make little difference as the higher ROF of the lighter guns would make up for the larger shells of the heavier ones.

Lion, I was thinking more of artillery, but your mortar suggestion is very interesting; I wonder if others would agree?

You may find some of the following of interest:
link

I also think you have to take more into account than calibre.

When looking at my own rules, I did some simple Wiki type searches and calculated weight of HE shell x rate of fire for a basic 'barrage' factors – what I call the 'bang for buck' factor – to classify weapons. Then, I thought of the value of heavy guns in dealing with specific things – like dug in troops, bunkers, armour, etc. – and reduced the cover effect of such things to the heavier stuff. It feels right and seems to work.

In point of note, I class 25pdrs as one class lighter than German 10.5cm. However, this is outweighed by battery size (8 guns Vs 4) so, at the scale I play, they hit with equal effect in practice.

The thing about mortars is the high HE content Vs the fact that the shells are surface, as opposed to sub-surface, detonations. Accurate + High content HE + High ROF = Superb Vs troops in the open. Pretty rubbish Vs anything with a decent 'roof' / dug-in though, because all of the power goes upward and sideways at the surface – arty shells bury themselves quite deeply before exploding; this is the primary reason heavy artillery was prefered to lighter artillery in WW1. I think this factor should not be forgotten.

calculated weight of HE shell x rate of fire for a basic 'barrage' factors – what I call the 'bang for buck' factor – to classify weapons.

This sounds like a rather sensible approach to me. And giving heavy guns some bonuses against special targets also sounds like a good idea.

However, this is outweighed by battery size (8 guns Vs 4) so, at the scale I play, they hit with equal effect in practice.

I was under the impression that the British 25 pounder troops could fire at their own separate targets when needed. In this case, would it make sense to make the troop (rather than battery) the basic "tactical" unit for 25 pounders?

I was under the impression that the British 25 pounder troops could fire at their own separate targets when needed. In this case, would it make sense to make the troop (rather than battery) the basic "tactical" unit for 25 pounders?

With the scale of battles I play, 25pdrs tend to be deployed by the regiment and having three firing batteries usually gives enough flexibility, though firing by troop is possible in my rules where required.

@Hornswaggler: That's completely the opposite of what I've read elsewhere from current active duty soldiers, so I really gotta question the idea that mortars are as effective as a cannon shell 20mm smaller.

120mm mortars are rated equal to 155mm guns, because the thinner mortar shell gives a bursting charge equal or greater than the 155mm.

From memory (and I'm happy to be corrected), I think most German field artillery (10.5cm and 15cm) was standardised on the four gun battery. Heavy stuff, Corps stuff, and batteries of captured stuff, was more variable in strength.

120mm mortars are rated equal to 155mm guns, because the thinner mortar shell gives a bursting charge equal or greater than the 155mm.

That would probably be true if blast effect was the sole determinant of lethality. But it isn't, it also depends on the amount/weight of stuff flying around when the thing goes off. This argument is expanded in the link I provided and elsewhere. I also recall that we had a rather lengthy discussion a while back on this forum about the danger posed by blast effect alone.

From memory, most of the wargames rules I play rate the effectiveness of mortars lower than conventional artillery of similar calibre. This is certainly an over-simplification as the differences would vary depending on many factors and specific circumstances, but as a workable rule it seems ok to me.

A few random points…

I usually play with troops of 25pdrs instead of batteries, and might be a one way of reflecting higher ROF in rules which don't model ROF.

25pdrs generate lots of little bangs compared to 105s, 105s are better against things in cover, 150s are even more effective against pretty well anything. The really big stuff is needed for targets under concrete. All are equally suppressive however in that they encourage people to hide and take cover and/or obscure their vision with smoke, dust etc. This is modelled in varying ways in different rules.

Personally I tend to rate 25pds as having less casualty effect against targets in cover (foxholes, trenches etc, not hiding behind a bush) than the bigger stuff.

It partly depends on level of game of course.

A few random points…

I usually play with troops of 25pdrs instead of batteries, and might be a one way of reflecting higher ROF in rules which don't model ROF.

25pdrs generate lots of little bangs compared to 105s, 105s are better against things in cover, 150s are even more effective against pretty well anything. The really big stuff is needed for targets under concrete. All are equally suppressive however in that they encourage people to hide and take cover and/or obscure their vision with smoke, dust etc. This is modelled in varying ways in different rules.

Personally I tend to rate 25pds as having less casualty effect against targets in cover (foxholes, trenches etc, not hiding behind a bush) than the bigger stuff.

It partly depends on level of game of course.

German towed field artillery usually had four gun batteries, later in the war this sometimes dropped to three. On occasion (e.g. 10th SS PzAR at Arnhem), batteries were overstrength with six guns.

SP field batteries were usually six guns though.

That would probably be true if blast effect was the sole determinant of lethality. But it isn't, it also depends on the amount/weight of stuff flying around when the thing goes off.

I will have to agree that fragmentation tends to be the big killer with artillery and mortar fire. And to generate those flying fragments, you will need both metal in the shell and explosive inside. There is probably a roughly ideal ratio of metal to explosive to produce best fragmentation effect (for a given type of explosive).

For artillery proper, shells needed to be capable of withstanding the high pressures present in barrel, thus a thick metal cover was needed for protection and there was limited amount of space left inside that could be filled with explosives. With mortars, there was lower pressure present (due to shorter range and longer firing angle), and thus a thinner outer layer was possible and more space was left inside, and thus designers had more room to play with.

That said, if the traditional design for artillery proper provided best explosive-to-metal ratio, why did the mortar shell designers go for a higher ratio? By the end of WWI, everybody should have been pretty aware of the importance of fragmentation effects. And in the interwar era there were two decades of time to test different shell compositions to determine their fragmentation effects.

Griefbringer wrote:

There is probably a roughly ideal ratio of metal to explosive to produce best fragmentation effect (for a given type of explosive).
[…]
That said, if the traditional design for artillery proper provided best explosive-to-metal ratio, why did the mortar shell designers go for a higher ratio? By the end of WWI, everybody should have been pretty aware of the importance of fragmentation effects. And in the interwar era there were two decades of time to test different shell compositions to determine their fragmentation effects.

You are quite right that there is an ideal charge/casing ratio for the infliction of personnel casualties. You are also quite right in pointing out the need for artillery shells to be strong enough to resist firing stresses. This is the problem that ensures that shells invariably have more steel and less charge than the ideal ratio. What is not generally realised is just how tiny a fragment is needed to produce incapacitating effects -- a gram is more than enough when propelled at the speeds produced by HE.

Mortars and rockets are capable of getting closer to the ideal ratio simply because the firing stresses are lower. This also explains why, in WW2, American shell were, pound for pound, more effective than British shell -- as Nigel's artillery pages explain, the British decision to user lower-grade steel meant that they needed thicker walls, and were thus even further from the ideal charge/casing ratio.

Some mortar bombs are considerably more effective thanks to their casings being made of cast iron, which produces much finer fragmentation than does steel.

Another factor militating in favour of mortars is their generally higher angle of fall. The fragmentation pattern of an HE burst is the result of three fragment sprays. The nose and tail sprays, cones of fragments projected before and behind the point of burst, account for maybe a fifth of the fragments. The bulk are in the side spray, an expanding doughnut of steel shards projected forward along the shell's line fo flight. The intersection of this expanding doughnut with the ground plance produces the "butterfly-wing" pattern characteristic of shell bursts. The steeper the shell drops, the more favourable the angle for this doughnut to sweep a greater area. This is why gunners prefer fire in the upper register when possible, as it can produce a better fragmentation pattern from the same shell.

Rockets and mortars can also include controlled fragmentation mechanisms, such as notched wire or pre-formed fragments, which tend not to be used in artillery shells, although I understand that pearlitic steels are supposed to improve fragmentation.

All the best,

John.

What is not generally realised is just how tiny a fragment is needed to produce incapacitating effects -- a gram is more than enough when propelled at the speeds produced by HE.

And this is the reason why helmets made a reappearance on battlefields during WWI – even relatively small fragment could cause serious injury to the head. And later on also flak vests would be introduced to protect the vulnerable central body from shrapnel.

Back to the original topic of 25 pounders, my understanding is that in the British doctrine divisional field artillery (25 pounders) was primarily meant to suppress and disrupt enemy, with casualties being an added bonus. And if heavier pounding was needed, there were bigger pieces available at the corps level.

For suppressive fire, 25 pounder probably packed enough punch – especially when combined with the high rate of fire and large number of tubes. Actually, if using late-WWI style creeping barrage on offensive, with infantry following close behind, limited explosions could be an advantage since they would cause less danger to the friendly infantry.

Some other things to consider:
Germans used 105mm in their assault guns because the rule of thumb was 2 rounds to take down an average house. And 150mm because one round to take down same house.

Mortars size of 120mm considered heavy enough to penetrate roof of building/house to damage interior.

Some great info here. I think there are two main type of artillery missions: Suppression and Destruction. A destruction barrage would normally be fired on a converged sheaf at a point target and generally takes a lot of ammo and time to establish. The Soviets have many formulas for this. I think destruction barrages by heavy/medium artillery are outside the scope of most squad/platoon based games because of the amount of time and why bother having a game where arty kills all of the targets.

Suppression missions would be relevant to squad/platoon games. They are normally fired in open sheafs with the idea of keeping the enemy heads down while the attackers get as close as they can before assaulting. I like Ditto's idea of leaving a sheaf in place and checking if the targets moves. This is pretty realistic and playable. I like it. One thing it appears most games don't account for is the timing of the barrage. A suppression barrage with upper level arty (medium and heavy)would normally be lifted at a specific time for the infantry/armor to attack. If the timing was off and the barrage lifted too early the defenders could emerge from their hiding and stop the attack. If the barrage lasted longer than expected the attackers could be hit by friendly fire. The last scene in the movie "Galipolli" illustrates this. There could be some type of way to abstract this to start a game with the attackers starting the game at a certain distance from the enemy depending on the effectiveness/timing of the barrage. This would be playable and accurate and speed up a game getting to the best part (the assault at close range) quickly. After lifting the barrage it would normally be moved further in towards the enemy disrupting any reserves and giving a DRM to reserve arrival. Ammo availability may prevent a rolling barrage and dictate the length/effectiveness of a suppression barrage. In the bigger picture it would depend on the type of attack and amount of time for planning. A Meeting Engagement would severely limit indirect fire from medium and heavy arty. A Planned Assault would have them available.

I think mortars at Company (light) and Battalion (medium) level would be targeted mostly against point targets in a converged sheaf. Firing an expanded sheaf with light mortars could be possible because of the high rate of fire but I haven't read very many accounts of that being used. 50mm and 60mm mortars could fire using direct observation making them very effective against any point targets without overhead cover even though a small caliber. At least for suppression.

Mortar barrages can have a very variable effect depending on ammo availability. A battery of two 60mm mortars could put down a barrage of up to 40 rounds in one minute (but for a short period) with the gunner moving the point of impact a little each round or attempting to keep them on one point of aim. However, setting up a light mortar in mud will mean a very dispersed barrage. Observing and adjusting each round limits the ROF to about 5-6 rounds/minute mainly because of time of flight.

John Salt makes a good point about individual round sheafs. I have not seen ant game that uses butterfly sheafs for HE rounds, especially for direct fire HE. If you have a game plotting individual arty rounds you could use these sheafs getting more realism without any playability degrade. All direct fire HE would use butterfly type sheafs.

Final Protective Fire from light mortars is something altogether different and very important in squad/platoon based games and don't seem to be modeled by war games rules (I may be wrong, let me know which ones do) coordinating with infantry Final Protective Fire.

One more point for arty is fuzing. Quick Fuses are good for targets above ground level and bad against targets with thick overhead cover. Delayed fuzing is bad against targets in the open but great against overhead cover or underground. This difference would be as low as 80-82mm mortars. Delayed fuses allow penetration through roofs, quick fuses would not be as good.

Wolfhag

Wolfhag wrote:

One more point for arty is fuzing. Quick Fuses are good for targets above ground level and bad against targets with thick overhead cover. Delayed fuzing is bad against targets in the open but great against overhead cover or underground. This difference would be as low as 80-82mm mortars. Delayed fuses allow penetration through roofs, quick fuses would not be as good.

Fuzing adds a good deal of richness to the problem that I have never seen properly represented in wargames.

A fair assumption, for the kind of open mobile actions wargamers tende to favour, is that most artillery fire will be HE fuzed superquick to produce groundbursts. As far as I know, most rockets and mortar bombs were also fuzed superquick. However, tube artillery has a lot more options.

Airbursts are more effective against troops without overhead cover than are groundburts,and there are several ways to obtain these. A time fuze is the obvious way, and for time fire mechanical (clockwork) time fuzes are I think generally more accurate than pyrotechnic (powder-train) time fuzes. AA guns were generally equipped with mechanical time fuzes. The Allies in NWE during the late war period, when there were few air targets left, employed AA in the ground role, and the combination of rapid rate of fire, supersonically-arriving shell and airbursts was considered very useful, although the low trajectory and high velocity meant quite a long 50% zone.

VT (proximity) fuzes were available only for the Western Allies for 1945, and these give a more reliable burst height than mechanical or pyrotechnic time.

Another way to obtain airbursts is by ricochet fire, which requires a reliable delay fuze with graze action. US artillery thought much of this technique; the RA tended not to use it, I suspect because of inferior fuze reliability.

Delay fuzes are also needed for demolishing houses or attacking entrenchments by mine action. Obviously a subterranean burst will produce much less in the way of lethal fragments above ground. One highly-specific task for which delay fuzes were necessary, as discussed in a WW2 OR paper, was shooting down factory chimneys, which make a good elevated OP for the other side, and require a surprising quantity of medium shell to demolish.

Exceptions I am aware of to the general rule that rockets and mortars were only fuzed superquick are the 21cm NbW 42, which had the option of a delay fuze, and the US 81mm "heavy" mortar bomb, which had a delay fuze specifically to penetrate house roofs (which otherwise would normally keep 81mm mortars out pretty well). There is also that oddity, the German 8cm WGr "bouncng betty" bomb, which produced an airburst by a two-stage process, an airburst charge being launched after the bomb's impact. I have not been able to find any numerical information on how effective this was.

All the best,

John.

"gainst troops in cover – which I assumed meant dug in troops, though it could also mean guys taking cover in "lumpy round""

Yes, I meant protective cover, as in foxholes or trenches.

Crinkly terrain is a lot less effective against indirect fire than it is against direct small arms fire as natural cover is often very directional. (so the ground undulation protects you from bullets from the front, but not the shell that lands behind you).

I have a rather tragic photo sequence from WW1 showing just that happening to a French infantry platoon. One minute they are cheerily taking cover behind the earth banks each side of a road, the next it is a charnel house.

I read somewhere that creeping barrages as used in late WW1 were most effective when the following infantry took about 10% casualties from their own barrage. If they were to far forward they would take higher casualties from friendly fire and if they hung back too much the enemy would recover and inflict higher casualties in defensive fire. I guess it sucked being an infantryman on the attack!

Thre is too much attention paid by wargamers to the calibre of a gun and its dammage. If you read the upen source US military manual then you will find that for typical wargames targets you can achive the same effect over an area whether it is 155's or 81mm mortars. This is on the basis that while a 155mm shell has an immence power it is very unlikely to achive a direct hit on anything as the available ammunition and rate of fire is very low. In addition the yield (effective HE per pound of shell) guns are worse than mortars as they need to accelerate the shell faster using more of the shels overall weight on propulsion. With an 81mm mortar you get a lot more shells for your given weight so more chance of a close landing and hence equal dammage.

The US planning sheets note for a given dammage level, how many 155 shells to suppress a platoon in the open to how many 81mm mortars. Someting like 2, 155 shells vs 8, 81mm shells. The big advantage of guns is long range. Artillery weapons are not ideal point target weapons as that generally is not there main purpose. Plotting unlikely direct hit dammage is proably a set of rules too far. Too many rules and wargames time taken up for too little gain.

Just because 1 direct hit of a 155 on a tank could do a lot of dammage does not mean it will happen. Tigers were destroyed by artiller or at least put out of action over some hours of shelling but only because they were put and told to stay in an unsuitable positions for 12 hrs! Not a typical wargames position and hence not worth the effort.

Back to the OP, Battlefront\Fire & Fury got around it by using the larger template size associated with the 105s but with slightly lower factors. That works well to allow 25Pdr artillery to suppress\disorder as the doctrine dictated, without making them too powerful

Leadgend wrote:

I read somewhere that creeping barrages as used in late WW1 were most effective when the following infantry took about 10% casualties from their own barrage.

I believe that the original French WW1 guideline was that 10% of your total casualties should be from friendly dropshorts. That's a different thing from taking 10% casualties from them (at least, if you have any soldeirs left).

All the best,

John.

I'm going to do similar for the odd-man out 122mm Soviet size, 155 AoE and lower effects – or do folks think that a 122mm battery should just be treated like a 105 battery?

I think that I'd treat 122mm howitzers the same as 105s, maybe give them a bump in their ability to punch cover.

FWIW, Flames of War gives the 122mm a 3+ firepower (ability to hurt dug-in troops), one point better than the 4+ of the 105mm guns.

I don't know how Crossfire handles arty, but I'm sure there would be an easy way to give the 122mm guns a slight boost over the 105s (assuming that you want to go to that much detail).

John, yes, that's what I meant to say, 10% of their casualties.

Ditto been busy on this one. Us manual says that if you are in a barrage you need to get out as soon as possible to replace the arials. Some minor indirect dammage is possible. Some tigers were taken ou by HE but they were obliged to stay in the open all night and get shelled periodically. The general observation from tankers was that they were pretty much immune to barrage fire when driving through. From what I read even the bombs on Caen did not do that much dammage to the troops although it upset them (and our own when we missed them).

Much of the debate here I think is distorted by not considering net charge delivery. That is for a given weight of shells delivered to a site. How much HE falls on the terget. Big guns g#have longer ranges so have nore charge. Their yeild is not as good as a mortar.

On direct fire it is a problem that needs very careful thoght. If artillery was that good at fixed defenbces we would not have had engineering vehicals for this. Shelling "individual" houses is not neccassarily realistic in a wargame. Even MG which is 1:1 for vehicals has to accept that the area taken up by one house is actualy getting on for 25 houses. Trying to destroy 25 houses with an assult gun would be impossible I suspect it wold be lukcy to have a full load of 50 shells to waste on one "wargame house". This is why we shoot at the contents not the actaul house unless with a demolition gun.

There could be some type of way to abstract this to start a game with the attackers starting the game at a certain distance from the enemy depending on the effectiveness/timing of the barrage.

I've done this in a WWI game very successfully – a simple die roll determining how far the attackers were from their own trenches before the enemy could react to them.