81mm vs 75mm

[offtaskagain]

Why does the 75mm artillery get a 39 blast whereas the larger 81mm gets only 18? Wouldn't the 81 be higher because it's bigger and low velocity so the casing doesn't need to be so thick? Same thing with the 150mm inf gun. Or is the better fragmenting modeled and I just don't notice it. Search takes too long, so please forgive me for bringing up old stuff.

[Stalins Organ]

Mortar ronuds are lighter than the same calibre of artillery rounds, although I don't have the figures on me.

[Kiltie Lad]

I've noticed a lot more air bursts with the 81mm mortar, so I'll wager its the trajectory and the air burst factor that make it so tuff.

[Seanachai]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Mike the bike:

Mortar ronuds are lighter than the same calibre of artillery rounds, although I don't have the figures on me.<HR></BLOCKQUOTE>

Mike is roughly right, and some actually knowledgeable person will be along shortly to give you the exact numbers, but calibre doesn't equate with shell weight. Artillery, by benefit of having more propellant 'punch' than a mortar, can loft a far heavier shell with more explosive matter over greater distances (in the process narrowing the muzzle width in the pursuit of velocity/distance and accuracy, while still retaining a heavier shell). Mortars, with far less propellant power, sacrifice the velocity/distance aspect and have to expand the diameter of the shell to achieve a significant payload, while still remaining lighter than the average artillery shell.

Just a layman's explanation, and garnered totally from reading I've done elsewhere on this site.

[JasonC]

"the casing doesn't need to be so thick?"

That is quite true. And it is not at all clear the CM figures are reasonable.

The 75mm shells are much bigger objects. In pure weight terms, they are twice the size of the 81mm rounds, because they are longer and driven by a larger powder charge, etc. But the bursting charges of both are on the order of 1 lb (.5 kg plus or minus), because of the thicker shell walls needed for the 75mm.

Incidentally, CM gives the British 3" mortar a 26 blast rating. That may be a more accurate ballpark for medium mortars, and it is not in the least clear the 3" deserves a much better rating than the 81mm or the US and Germany.

There are arguments about that from tests and sharpnel type and the quality of steel used and what not. There is also considerable variation and dispute over the typical burst effects of 75mm, which may vary considerably with the types of shell involved. E.g. some German 75mm tank gun HE shells had 454 gram bursting charge. Another type seems to have had a 860 gram bursting charge. Some of the charges are amatol mix, some are more powerful pure TNT.

That a 75mm artillery round is a much bigger thing that an 81mm mortar round is quite true and seems to be behind the CM figures. It is entirely possible a more realistic assessment based on all factors, would have the two types roughly comparable in blast effect.

It is a vexed and disputed question, and you are right to challenge or be skeptical of the way it is in CM. But what the exact or right relation would be, is very much up in the air. And BTS seems to be reluctant to change something when the "to what?" question cannot be satisfactorily answered. Entirely reasonable, but not completely satisfying.

[Simon Fox]

<BLOCKQUOTE>quote:</font><HR>Incidentally, CM gives the British 3" mortar a 26 blast rating. That may be a more accurate ballpark for medium mortars, and it is not in the least clear to me the 3" deserves a much better rating than the 81mm or the US and Germany.<HR></BLOCKQUOTE>I take it that that is what you mean? Otherwise you are a presumer of Weissian proportions

[Jarmo]

There seem to be two "odd" blast figures in CM mortars.

The first being british 3" amd the second the greman 120mm.

The german 120mm having almost twice the blast of the

british 120mm mortar. Way stronger than 105mm gun.

That's not to say the figures are incorrect, just interesting.

[Simon Fox]

Absolutely and when you know the reasons it makes you that much more confident that Steve and Charles did a pretty good job on their research. Like the difference between the US and UK 4.2 in mortars.

[Redwolf]

Speaking of it, why is the 4.5 gun FO more expensive for the U.S. than for the British? Same blast and ammo.

[Redwolf]

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

Speaking of it, why is the 4.5 gun FO more expensive for the U.S. than for the British? Same blast and ammo.<HR></BLOCKQUOTE>

Found it myself. It's faster.

Anyone would like to explain the 4.2" mtr issue and this one?

[Fishu]

I know one thing, I do like mortars, even if weaker shells.

Faster response and when uses those, there will be bunch of those coming all around the target, making infantry targets suppress more.

(twice as fast call in time than what the howitzers have and more rounds)

Though, I like more of 105mm and bigger artillery when attacking, but when in defence or meeting, I like more of mortars due to faster response time (can call in shells faster on rapidly advancing troops, plus suppress them more with quicker firing adjustments)

[CombinedArms]

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

Anyone would like to explain the 4.2" mtr issue ?<HR></BLOCKQUOTE>

Here's a detailed discussion of the 4.2" mtr from another artillery thread that I recently happened to start ("So What's 4.5 inch artillery?"). The thread, which I highly recommend to all arty buffs, also has much detailed discussion of Brit vs. US 4.5 guns and a lot more. Thanks to JasonC for quoted material:

I had asked, in the initial post on the thread: "what were 4.2 chemical mortars?"

JasonC answered:

"These were heavy mortars intended for chemical warfare, gas warfare, should it break out. I.e. if the Germans used gas, they would be the primary or initial means of replying in kind with poison gas shells. In the absence of chemical warfare, they were optimised to perform smoke missions, both ordinary smoke and white phosphorous.

Originally there was no HE shell for them, but an artillery officer assign to them developed one independently in late 1942. From 1943 on, they were therefore able to provide HE support to the infantry as well as smoke missions.

There were 16 "battalions" of them serving in the ETO, plus 2 in Italy and 6 in the Pacific. These battalions were bigger than standard artillery battalions because they used the infantry, mortar structure and unit size names. That is, 4 mortars were a "platoon", and 12 a "company", instead of those being called batteries and battalions as the same number of tubes would be called in the field artillery. Ordinary practice was to assign 1 company of them (12 mortars) to each infantry division."

ts9 also linked us to a URL providing:

"Everything you ever wanted to know about the 4.2" chemical mortar but were afraid to ask: www.4point2.org

[argie]

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

"the casing doesn't need to be so thick?"

That is quite true. And it is not at all clear the CM figures are reasonable.

The 75mm shells are much bigger objects. In pure weight terms, they are twice the size of the 81mm rounds, because they are longer and driven by a larger powder charge, etc. But the bursting charges of both are on the order of 1 lb (.5 kg plus or minus), because of the thicker shell walls needed for the 75mm.

Incidentally, CM gives the British 3" mortar a 26 blast rating. That may be a more accurate ballpark for medium mortars, and it is not in the least clear the 3" deserves a much better rating than the 81mm or the US and Germany.

There are arguments about that from tests and sharpnel type and the quality of steel used and what not. There is also considerable variation and dispute over the typical burst effects of 75mm, which may vary considerably with the types of shell involved. E.g. some German 75mm tank gun HE shells had 454 gram bursting charge. Another type seems to have had a 860 gram bursting charge. Some of the charges are amatol mix, some are more powerful pure TNT.

That a 75mm artillery round is a much bigger thing that an 81mm mortar round is quite true and seems to be behind the CM figures. It is entirely possible a more realistic assessment based on all factors, would have the two types roughly comparable in blast effect.

It is a vexed and disputed question, and you are right to challenge or be skeptical of the way it is in CM. But what the exact or right relation would be, is very much up in the air. And BTS seems to be reluctant to change something when the "to what?" question cannot be satisfactorily answered. Entirely reasonable, but not completely satisfying.<HR></BLOCKQUOTE>

Weight of the shell of USA 81mm: 3.12kg

UK 3" = 4.54

Ger 81mm = 3.5 kg

USA 4.2 = 14.5 kg

UK 4.2 = 9.07 kg

[Redwolf]

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

Here's a detailed discussion of the 4.2" mtr from another artillery thread that I recently happened to start ("So What's 4.5 inch artillery?").<HR></BLOCKQUOTE>

I read that thread. However, the question I had is what the British 4.2 mortars are and what makes them so different from the U.S. 4.2".

Thanks.

[Simon Fox]

The British 4.2" mortar (107mm)is a basic heavy Stokes type mortar, a scaled up version of the 3" mortar and similar in design to the 81mm/82mm mortars floating around. http://www.riv.co.nz/rnza/hist/mortar/mort16.htm

The US 4.2" is a different beasty all together, having a rifled barrel, a totally different round (larger) and a greater range. http://www.riv.co.nz/rnza/hist/mortar/mort17.htm

[Redwolf]

Thanks, Simon, exactly what I wondered about.

[JasonC]

"Weight of the shell of USA 81mm: 3.12kg"

There was more than one kind of 81mm shell. That may have been the most common, but there were also "heavy HE" that were around 12 lbs rather than 7 lbs, because longer. Shorter range, more blast. The two types straddle the weight of the Brit 3".

I am sure there were materials differences like type of iron or steel used, and also different weights of bursting charges, and types of bursting charges (TNT vs. amatol, etc).

The largest mystery remains why 81mm mortar rounds with bursting charges on the order of 1 lb, have much lower blast than 75mm rounds with bursting charges of about the same weight.

And another one is why the Brit 3" on map mortar pays for its higher blast rating (proportionally - 26/19 = 1.37, cost is 36 vs. 26 = 1.38) - but does not seem to pay for twice the HE rounds per mortar, or more. It thus winds up giving twice or more the total HE, for the same cost as other nation's 81mm on map mortars. Since costs are supposed to reflect only combat effectiveness, it would seem the designers believe twice the ammo load isn't an edge, which is naive to say the least.

[ 05-09-2001: Message edited by: JasonC ]

[Redwolf]

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

And another one is why the Brit 3" on map mortar pays for its higher blast rating (proportionally - 26/19 = 1.37, cost is 36 vs. 26 = 1.38) - but does not seem to pay for twice the HE rounds per mortar, or more. It thus winds up giving twice or more the total HE, for the same cost as other nation's 81mm on map mortars. Since costs are supposed to reflect only combat effectiveness, it would seem the designers believe twice the ammo load isn't an edge, which is naive to say the least.

<HR></BLOCKQUOTE>

Hey, don't tell my secret weapons to everyone

I guess that the cost of on-map mortars reflect that a mortar is easy to knock out, thus a higher ammo load may not be as useful as multiplication of blast implys. The same blast sum distributed to several tubes is more useful, i.e. to fire smoke and supression at the same time.

I could imagine that CM models the 3" mortar as easier to spot (like the infantry guns), but I didn't check that.

In any case, the 3" mortar is comparably cheaper than the 81mm because:

- it is slower

- it has a higher transport class, it doesn't fit into a stuart kangaroo and only one can be placed in a M5A1 halftrack, a big disadvantage for me

Question: the 3" mortar in CMBO knocks out Pz IV and StuGs with top penetration. Is that historically correct?

[Battlefront.com]

JasonC wrote:

<BLOCKQUOTE>quote:</font><HR>The largest mystery remains why 81mm mortar rounds with bursting charges on the order of 1 lb, have much lower blast than 75mm rounds with bursting charges of about the same weight.<HR></BLOCKQUOTE>

Remember the blast effect is not just about the ability to take out soft targets, but also its ability to damage hard ones. Artillery shells had thicker casings and therefore more potential to damage whatever it hit (vehicle, house, etc.). Also, IIRC shrapnel is dispersed over a larger area due to the larger mass of the pieces.

We have been over and over the blast effect stuff in the past many many times. We are more than satisfied that we have it right. Artillery is superior to mortars in terms of individual shells of roughly the same size. This is one of the primary reasons we still use artillery today instead of just mortars. The are different weapons with different capabilities, and therefore each has its own set of + and - factors.

<BLOCKQUOTE>quote:</font><HR>Since costs are supposed to reflect only combat effectiveness, it would seem the designers believe twice the ammo load isn't an edge, which is naive to say the least.<HR></BLOCKQUOTE>

No, it would be naive to think that the designers made an obvious mistake like this and that nobody has picked up on in almost a year's worth of playing. The answer is that the designers accounted for the fact that the 81mm teams have 2 more men than the 3" mortars, meaning that they have greater staying power in the field. In other words, it is much easier to knock out or immobilize a 3" mortar than a 81mm. Also, ammo counts go down VERY fast if the 3" mortar takes casualties and then tries to move.

Steve

[ 05-10-2001: Message edited by: Big Time Software ]

[IPA]

AFAIK -

British Line Infantry 3" Mortar crew - 4-5 men plus accompanying transport/driver (usually a universal carrier)

British Airborne 3" Mortar crew - 8 men. One carried the tube, one the bipod, one the base plate, 5 others carried 7 bombs each. Reserve ammunition would be carried in the Support Co handcarts and jeeps.

Peter

[Battlefront.com]

IPA,

I would have to check (the research was done over a year and a half ago ) but I think the 3 man example in CM is a reflection on likely strength, not official TO&E. Due to acute manpower shortages units were stripped of extra men whenever possible. A unit that was supposed to be transported by vehicle (and there were plenty of vehicles), and was not supposed to be engaged in short range front line action, would be a prime candidate for "slimming down". The extra men would have been moved to rifle and other high priority combat units. One example of this was organic AA units were generally disbanded by this point in the war, freeing up a large number of men for other duties more likely to be needed on a daily basis. However, the official TO&E, IIRC, did still specified AA units.

Whenever we felt there was compelling evidence of a widespread difference between theoretical TO&E and actual organization we leaned more towards what was more likely to be the case in the field. Other examples are higher number of SMGs for British Rifle Squads than they were officially supposed to have and less MP44s in German units than officially called for. Unless I am mistaken, this was the logic behind a lower head count for 3" mortars.

Steve

[Battlefront.com]

OK, I just asked Charles. From what he can recall (and it sounds very familiar to me) the reduction was due to the capacity of the Unviversal Carrier, to which these mortars were (exclusively by 1944?) assigned to. One man as dedicated driver, one as dedicated gunner, three for the actual mortar team. Total of 5 men. Yes, it would most likely be the case that the UC gunner and/or driver would hop out and help with setting up and firing, but for game reasons we can't have dual purpose men like this.

Steve

[IPA]

Steve,

For British line infantry, I'd have to agree that the below actual strength reasoning is justified. However, I was actually trying to use the accompanying transport as an explanation for the high ammo load out of 66 rounds in CM. Line Mortar crews, on a CM battlefield would have been very static. During the initial setting up of positions, the ammuntion would have possibly been unloaded into the weapons pits and then the transport pulled back to the rear/battalion HQ (out of harms way). On the other hand a Mortar crew could not have possibly moved that much ammo without transport or additional manpower. However, I can see that increasing the size of mortar crews would have increased the cries for gamey use of mortar crews as last resort infantry. I have to admit that my source for line crews, is Michael Dorosh's excellent website commentary on the organisation of a Commonwealth Infantry Battalion.

Now airborne units are a different matter. Support Companies (but not necessarily rifle companies) were sent into operations at full official TO&E strength. I have several sources too support this. Airborne units with limited transport, of course had to lug the whole lot around on foot. The very nature of airborne ops meant that mortar crews did have to be fairly mobile as the situation dictated. As such the full 8 man team would (unless absolutely necessary) have to stay with tube in case a move was needed and also to provide local defence. At Arnhem, once ammunition was expended, these crews did resort to infantry and gave a very good account of themselves.

I fully understand though, that airborne units are a very specific case and don't justify a change.

So to conclude, yes I would like see an increase in crew members specifically for airborne units. But on the other hand if anyone feels that the ammo load out is unfairly too high, go and reduce it yourself using the editor.

Thanks for taking time out to respond Steve, you must be very busy.

Peter

[ 05-10-2001: Message edited by: IPA ]

[ 05-10-2001: Message edited by: IPA ]

[Redwolf]

There was a 3" mtr mounted on a universal carrier. Anybody knows whether that could fire while the mortar was on the vehicle, like the U.S. mortars carrier halftracks?

Some pictures, but no answer: http://www.overkill82.freeserve.co.uk/LPC.html http://www.mapleleafup.org/vehicles/carriers/uc1.html http://home.att.net/~d.kuligowski/henkofholland/Au_mortar.jpg http://www.qualitycast.com/gb2046.htm

[Battlefront.com]

Hi Peter,

<BLOCKQUOTE>quote:</font><HR>During the initial setting up of positions, the ammuntion would have possibly been unloaded into the weapons pits and then the transport pulled back to the rear/battalion HQ (out of harms way). On the other hand a Mortar crew could not have possibly moved that much ammo without transport or additional manpower.<HR></BLOCKQUOTE>

True. This is just one of those areas where we run into problems in terms of simulation. What we really needed to do was have two different 3" mortar units, one at full strength (be it Airborne or line infantry) and one at "mobile" strength like we have now. The "mobile" one would start out with a full complement of ammo, but if moved would lose a good chunk of it. The full strength one could move on its own power with full ammo, whatever that might have been.

Of course, the discussion of headcounts doesn't have anything to do with the question of unit cost. If we had a 5 man 3" team it would, of course, be more expensive.

Steve