81mm mortar dispersion

[Apa]

The mortar really is quite accurate at close distances. At least modern 81mm mortars. And there hasn't been that much technological improvement, so I think my experience using modern mortars applies to WWII mortars also.

Now, if a mortar under fire should have the same accuracy? No, it should not. You need to fine tune the tube if you want good accuracy. To do that, you need to be in a crouching position for a couple of seconds. Actually, you need two man doing that. Not easy to do while under fire.

Another issue is that in general I would like that area fire would be much more _area_ fire. Currently it is too easy to use your semi-borg abilities to area fire known enemy positions. The area fire should hit a much larger area.

My idea would be to force area fire to an area of maybe 1/25 of range radius circle. So, at 100m you could are fire at most to 4 meter radius circle, or one action spot. At 200m, to 8m radius circle, at 1000m to 40m radius circle. I think there is currently some effort to this, but the area is just too small, and the pattern too centered. This would naturally need a lot of testing to get the minimum circle radius correct.

In my opinion, such area fire would be vastly more realistic than the current "spon-on" area fire. This would have a nice effect on the tactic of "use tanks sitting at the other side of the map insta-area-firing anything that is spotted".

In addition, being able to set your MGs to area fire at a larger are than just one action spot would be a nice feature.

[Michael Emrys]

Caveat being GPS was a novelty just coming in as I was going out, so power packs might be a lot lighter nowadays.

I would imagine so if smart phones now feature it. They might not be as precise as mil stand, but you get the idea.

Michael

[wombat_of_war]

im not sure if it will be useful and im having trouble making sense of the data but ive got Terminal Ballistic Data Vol 3 - Bombs Artillery Mortar Fire Rockets - 1945 on my site.. direct link for the document to download is https://docs.google.com/leaf?id=0B08mkmHC8WBaMTdhY2NhYjItM2Q3NS00OGMzLTg4ZDktODI4MTY1NTIxMzg4&hl=en_GB hope it will help

[JonS]

Very useful, thanks ... but probably not for this specific discussion

[DavidFields]

+1 JasonC remarks.

This is not only an issue of what can be done with a mortar, but how they were used in reality.m Maybe putting a mortar shell in a pickle jar from a large distance is possible, but that, as I understand, is not how they were used.

Granted, it is in part a philosophical issue. Should one be able to use mortars in a more, arguably, more effective way than they were used in WW2? But then, even with relative spotting, it is unclear to me that a routine sniper shot with a mortar is very realistic.

[Again I lament that time is passing too far from WW2, and hence the "obvious" becomes increasingly obscure]

[c3k]

I still have vivid memories of 2 squads in halftracks being wiped out by a 60mm mortar which dropped rounds into each of the passenger compartments. That was not pretty. The range was about 150m. It took just a few rounds to nail each halftrack. (That's my memory talking, not necessarily accurate.) The term "rage quit" suddenly had a visceral meaning to me.

[Apa]

I still have vivid memories of 2 squads in halftracks being wiped out by a 60mm mortar which dropped rounds into each of the passenger compartments. That was not pretty. The range was about 150m. It took just a few rounds to nail each halftrack. (That's my memory talking, not necessarily accurate.) The term "rage quit" suddenly had a visceral meaning to me.

This particular instance could be solved by improved TacAI. TacAI should move the halftrack into safety in such situations. Of course, that movement could cause a "rage quit" if for example the halftrack decides to move at the wrong time or into the view of a Panther.

I don't know about the rest of you, but I really do think that having a minimum area for area fire and indirect fire would solve many problems. The are could be based on range, C&C status and if the firing unit knows that enemy units are in the target area.

If the target radius had been 8m (just for example), even that would have changed the results in your example.

If the vehicle was in view of the 60mm mortar, then there of course should be no minimum target area. Then the question is if the mortar was too accurate. My experience says that there isn't any big mistake in the accuracy. TacAI should have moved the vehicle, but this might be hard to program in a way that solves more problems than it causes.

I think we need to ask MythBuster if you really can hit a bucket with a mortar...

[YankeeDog]

This particular instance could be solved by improved TacAI. TacAI should move the halftrack into safety in such situations. ...

I think this feature is already in the game -- Working off my increasingly faulty memory here, but I am pretty sure I have seen a "self-preservation" routine kick in which involves vehicles attempting to move out from under artillery fire of their own accord.

Unfortunately, my CMBN-capable computer is down at the moment, so I can't verify my recollection.

Anyway, if my recollection is correct, then it may be that this behavior needs tweaking one way or another. But, as you note, balancing these kinds of behaviors can be tricky because vehicles relocating of their on their own initiative can potentially get them into even worse trouble than they are currently. They shouldn't necessarily be jumping off at the first nearby explosion.

[Steiner14]

Why change another unit's behaviour, instead of solving the root of the problem of too accurate mortars?

Mortar units must have been the most decorated units in the whole war. Not for inflicting a certain amount of casualties, which seems to be peanuts, but for taking out ATGs, HMGs and armoured vehicles in the dozens on their own with a probability of success of 100% in max. 2 minutes with only 40 genades and without almost no risk of own losses.

Only losers need tanks for attacks. Instead of a tank company, give me ten light mortars and a walk in the park is guaranteed. :mad:

[YankeeDog]

OK, so since there still seems to be some question as to exactly how accurate WWII-era small mortars were at short range, I did some digging through some old files I had archived. I knew I had some 60mm range tables somewhere...

Turns out, I don't have the WWII-era range tables, but I do have US Army publication FT-60-L-1 "Firing Tables, Mortar, M19 and M2", dated March 1951. So this is not WWII, but it's pretty darn close. As far as I know, there weren't any huge advances in light mortar technology between the end of WWII and 1951.

Anyway, here are some samples of the "Probable Error" values listed in this publication. The publication doesn't specifically say so, but I would assume that these values represent 50% CEP (= 50% of shells fired will impact within distance cited of the Mean Point of Impact, and nearly all shells fired will fall within distance cited x 3), as this is pretty much standard for this sort of thing.

In all cases, I have quoted the charge setting(s) that give the best accuracy for the range cited. I have quoted 2 charge settings were overall accuracy is similar, but there is a difference in the details of range error vs. bearing error.

100 yards

(Charge 0)

range: 1 yard

bearing: 2 yards

200 yards

(Charge 0)

range: 5 yards

bearing: 2 yards

(Charge 1)

range: 4 yards

bearing: 4 yards

300 yards

(Charge 0)

range: 7 yards

bearing: 2 yards

(Charge 1)

range: 6 yards

bearing: 4 yards

400 yards

(Charge 1)

range: 8 yards

bearing: 4 yards

(Charge 2)

range: 7 yards

bearing: 6 yards

500 yards

(Charge 1)

range: 10 yards

bearing: 4 yards

(Charge 2)

range: 6 yards

bearing: 8 yards

Again, the publication doesn't specifically say so, but I would assume these figures are basically "benched" accuracy figures -- that is, under firing range conditions, with the weapon well grounded, no wind, etc. In other words, these figures are an estimate of the theoretical accuracy of the weapons system under ideal conditions.

Nevertheless, I think they do amply show that if you're talking about a 60mm mortar tossing bombs the length of a single bocage field, the weapon is pretty darn accurate. Maybe not accurate enough to drop a shell in a rain barrel in 2-3 shots, but definitely accurate enough that the mortar has a good shot at dropping at least one shot out of a dozen into a rain barrel at the ranges listed (assuming the mortar is perfectly zeroed on the barrel, which is a big assumption).

Please note I am not necessarily posting this as a rebuttal to any of JasonC's comments above -- "benched" accuracy of a weapons system on the firing range is one thing. Practical precision that a weapons system can achieve on the battlefield is quite another, and depends on many factors.

But I thought some hard data might be helpful for the discussion.

Cheers,

YD

EDIT to add: Since this thread was originally started about 81mm mortars, I did look for contemporary 81mm mortar tables as well, but unfortunately was not able to find any. However, it is likely that the Probable Error figures for 81mm mortars would be very similar at the ranges listed. This in a very important qualifier; for U.S. forces, at least, it would be rare for 81mm mortars to engage at ranges under 500 yards.

[JasonC]

c3k - the copy I have is from the 1970s. Post WW II, pre smart munitions or GPS guided anything. Standard indirect fire procedures, of the type use in Nam, Korea, or WW II, basically.

I hope that helps.

[JasonC]

YankeeDog - I agree the data are useful and thanks for providing it. But for anyone who thinks that means CMx2 is correct about typical mortar accuracy, I don't think so. Because by that reasoning, every rifle shot should hit within 1 inch of the aim point at 100 yards, and within 2 inches at 300 yards. Every shot on the battlefield should be a kill against a man sized target, even in cover, at CMx2 ranges. Rounds expended should equal men hit. Why not, if the inherent accuracy of a rifle is a group less than 2 inches across at all CMx2 ranges?

No see, the first problem with firing anything is the aiming accuracy, not the inherent dispersion of the weapon. Is the center of the shot-dispersion circle exactly aligned over the center of mass of the target? Answer, not it is not. In the case of high angle weapons, the biggest of those misses is the range, which without a laser range finder will not be estimated accurately. Instead the center of the circle the mortarman is trying to put on the target will be off by up to 50 meters.

Then he fires a shell, and has a 50 50 chance of missing by over 7 meters not from the point he wants to hit, but from the point he aimed at - over or under. And in reality it will be more than that, because he isn't on a firing range and there is wind and the round is in the air for 2 full seconds etc. All he sees about the result is whether it fell short or went long, and he makes a big correct - a 50 meter or so, in fact. Once he has an over and an under, he drops shells down the tube as fast as he can, and dust smoke and fragments spray all over the target area. He doesn't see or correct anything from those. The guys in the area of the beaten zone are all heads down in whatever cover they have by the time the 3rd round is going off.

A light mortar effectively pins an area maybe 60 meters across as a result. Pins, doesn't kill. Half the shells may be falling in the center radius of that area, but it is not centered over the intended target. It is centered over something or other - just as the 2 inch shot group you get on a bench rifle test is centered wherever on the paper target, not on the bullseye every time. But it doesn't much matter - because he's fired a dozen shells and each has a 15 yard burst radius, and each is randomly sprinkled around that area.

That is what "area weapon" means.

Now an 81mm is a much more powerful weapon because its inherent accuracy is just as high, but its bursting radius covers 5 times the area. And you still fire 2 of them at the same aim point pretty much as a minimum, and preferably 4 to 6 of them, and for a minute or two straight.

[JonS]

Anyway, here are some samples of the "Probable Error" values listed in this publication. The publication doesn't specifically say so, but I would assume that these values represent 50% CEP (= 50% of shells fired will impact within distance cited of the Mean Point of Impact, and nearly all shells fired will fall within distance cited x 3), as this is pretty much standard for this sort of thing.

Hmm. All the data of this kind that I've seen is that the PEr (Probable Error range) given is long of the target or short of the target. So to get the beaten zone you need to double it to get long and short,.

To give a specific example:

400 yards

(Charge 1)

range: 8 yards

bearing: 4 yards

The beaten zone in this case would be a rectangle 8 yards wide by 16 yards long, centred on the nominal point of aim.

[DavidFields]

We shall see how the 2inch and 3 inch mortars work in the Commonwealth Module. If the 2 inch mortars are accurate killers, that, to me, would be a problem.

JasonC seems to be absolutely correct, in my opinion, in his conceptual understanding of the mortar situation. My suspicion is there could be a similar conceptual quirk in the AFV hit data, were info may be used based on range data, whereas the acutal gunner may have a hard time estimating range, and may be trained to bracket.

I remember playing CM1 paratroop scenarios, where we were advised to stay at level 1, on the ground, viewing for the entire scenario. This, of course, is the more realistic way to view the battlefield--making it, wickedly, hard to estimate range or understand the tactical situation.

To me, this is less a criticism of CMBN than a "huh?, can we improve this?". It would seem fixable.

[Writing the above before JasonC's last post: after seeing his latest post, should the mortar impact zones be more oval, like CM1?]

[YankeeDog]

@JonS:

Completely agree with your points. And yes; what I was trying to say and perhaps not being very clear about is that the deviations are presumably long or short (or right/left, as applicable). That is, as you say a deviation of 8 yds. Is +/- 8 yds.

And @ JasonC: Yes; "benched" accuracy is a starting point, and definitely not what to expect under real combat conditions. However, I do think it is worth noting that 60mm mortars firing at short range in "direct lay" (i.e. where the mortar crew have direct LOS to the target point) in-game already exhibit deviation substantially greater than the figures I cited, so clearly BFC has already incorporated some sort of "combat conditions correction." Perhaps not enough, but something is there.

And, and the least, I think these figures indicate that If a 60mm mortar team is able to setup in direct LOS at a range of under 500 yds. to a target like an MG or Gun, and then the mortar is able to get off a couple of ranging shots more or less unsuppressed, then said MG or gun is in very big trouble.

With regards to direct-lay mortar usage in-game, my issue is more with the relative ease of setting up mortars this way in the game, rather than the accuracy. Every FM I have ever read that deals with small-unit mortar tactics heavily emphasizes the importance of keeping the mortars in defilade, out of direct LOS of the enemy, which suggests to me that the life expectancy of mortars in LOS of the enemy was usually not very good.

Indirect fire is a rather different topic. I have made comments on this before and JasonC's above I think are very good -- there seems to be no Mean Point of Impact deviation for indirect fires in CMBN right now, a shortcoming that has only a minor effect on heavier artillery with a larger danger zone, but is much more important for smaller ordnance.

Consider how effective indirect 60mm point fires would be in-game, if they used the CEP stats I cite above, but displaced the MPI 0-4 action spots in a random direction from the intended aim point. A few missons would be right on and very deadly, but at the other end, some fires would be 32m off-target and have very little effect on the intended aim point (considering the 50% lethality radius of a 60mm shell is usually considered to be about 15m, less against targets that are dug-in or have other good cover).

Which is, of course, why IRL they usually spread out indirect fires at least a bit from the theoretical tightest possible pattern, even when aiming at a point target -- to make sure at least some of the shells landed on or at least near the intended aim point.

I think there are at least a couple of different ways the game could be adjusted to reflect this. One way would be to simply add MPI error to point fires as I describe above, and let players learn why it's usually a bad idea to do a true point fire with a light mortar -- occasionally, you'd get lucky and the fire would be right on, but at least equally often, you'd just plain miss. A ~25m radius circular mission would therefore usually be a better choice.

Or, indirect point fires could simply be spread out a bit more. Technically less realistic, but simpler and easier to understand, especially for beginning players.

Cheers,

YD

[YankeeDog]

[Writing the above before JasonC's last post: after seeing his latest post, should the mortar impact zones be more oval, like CM1?]

Depends on the Range and charge setting -- see the probable errors I posted above and you can extrapolate what the impact patterns might look like. At some ranges, and especially at the extreme range of the mortar, the pattern is more oval. At some shorter range/charge settings, the pattern is nearly circular.

[JonS]

Indirect fire is a rather different topic. I have made comments on this before and JasonC's above I think are very good -- there seems to be no Mean Point of Impact deviation for indirect fires in CMBN right now, a shortcoming that has only a minor effect on heavier artillery with a larger danger zone, but is much more important for smaller ordnance.

Consider how effective indirect 60mm point fires would be in-game, if they used the CEP stats I cite above, but displaced the MPI 0-4 action spots in a random direction from the intended aim point. A few missons would be right on and very deadly, but at the other end, some fires would be 32m off-target and have very little effect on the intended aim point

except ... that's not indirect fire you're describing, it's blind or map fire. CMBN assumes, and indeed requires, that indirect fire be controlled by some kind of observer. The whole point of having the observer in the loop is to have them ensure the MPI and beaten zone is over the intended target. In principle, any clown should be able to eventually get the MPI centred where they want it. Clowny clowns will take a good long while, while non-clowns will get there in just a few rounds of adjustment. CMBN models this with variable lengths of time before the firing unit goes to FFE (the delay actually encompasses a couple of seperate issues, including navigating multiple C2 layers, but at least part of it relates to FO skill).

What CMBN doesn't model very well is not knowing where to put the MPI, which in The Real World is the single greatest issue facing FOs. CMBN doesn't model it very well because of the borg.

[YankeeDog]

@JonS:

I see your point. I think the point I am trying to make, and I think one of the points JasonC is trying to make, is that IRL mortar FOs almost never try to resolve the MPI to a granularity of less than 25m -- due to a variety of factors including observational error and inherent error probable of the weapon, it's very difficult to get the MPI certainty down to better than +/- 25m. Its theoretically possible with lots of spotting rounds, but not really practical. And this is very important for a weapons system with a a lethality area of less than 20m.

[Steiner14]

For the german mortars the Heeresdienstvorschriften should contain the important data:

8cm:

H.Dv. 102 Der schwere Granatwerfer 34 (8 cm) 1938

H.Dv. 104 Ausbildung (training) am s.Gr.W. 34

H.Dv. 119/951 Schußtabelle (shooting table) s.Gr.W. 34 (8 cm) 1942

5 cm:

H.Dv. 101 od. H.Dv. 145 Der leichte Granatwerfer 36 (5 cm) 1937

H.Dv. 103 Ausbildung am l. Gr.W. 36

H.Dv. 119/941 Schußtabelle

Too bad there seem to be no downloads on the net available.

[JonS]

I think the point I am trying to make, and I think one of the points JasonC is trying to make, is that IRL mortar FOs almost never try to resolve the MPI to a granularity of less than 25m

When bracketting for range OT, perhaps, but when adjusting for line I'd bet they sent corrections of less than 25m.

it's very difficult to get the MPI certainty down to better than +/- 25m. Its theoretically possible with lots of spotting rounds, but not really practical. And this is very important for a weapons system with a a lethality area of less than 20m.

Again, on range OT I agree (and 25m might even be too short ... I'd have thought 50m*), but not for line. The lethal area of a single round is less than 20m, but that doesn't matter too much because you should be firing more than one at a time anyway. The beaten zone of the individual barrel, and the beaten zone of the 3 x 60mm in a company should easily cover the interval between bracketting adjustments of +/-25m.

Jon

* on the other hand ... firing 60mm at relatively short range and at targets tyupically within what would be considered Danger Close ... yeah, I can see 25m.

[Rob Deans]

Hi everybody,

As this is a subject that is dear to my heart, I have followed this thread with interest. When the subject of "Probable Errors" came up I was most intrigued. I fear, however, that the term has been miss understood in this discussion. Please indulge me....

The mortar (or any indirect fire weapon) will simply not put all the rounds of a given mission on the same spot, not due to improper aiming (laying) but due to "mechanical" irregularities such as differences in propellant, irregularities in the barrel and small differences in weights and dimensions of the actual rounds to name a few. I state this only as a lead in to further explanation. The pattern that the rounds will land in will form an oval of varying dimensions based on range to impact (distance GT, or Gun-Target). More circular close in and stretching out to a long, (and relative to the length) slender oval at range. If a box is drawn around the complete beaten zone to encompass all fallen rounds it will, of course, give dimensions of width and length. It is these dimensions that form the basis of calculating the Probable Error or PE.

I won't go into more detail of ow the numbers are generated but in the reference below you can read to your hearts content. This "100 %" box is divided into 8 parts by length and by width giving 64 (total) "sub" boxes. The dimensions of each of these sub boxes is, of course, the same and they are the PE for range and deflection.

What does this mean for the game......? The figures that were quoted earlier for PE of the 60mm mortar...

To give a specific example:

400 yards

(Charge 1)

range: 8 yards

bearing: 4 yards

What this means is that at 400 yds on charge 1, ALL of the rounds in a given mission (and of course this is all based on best case firing conditions) will land in a box that is 64 yds long by 32 yds wide. Remember, that means it will miss the target by no more that 16 yds left or right and 32 yds plus or minus) Now, the concentration of these rounds will naturally be more tightly grouped towards the centre of the 100% box (or mean point of impact), in fact within the centre "4 PE x4 PE" box. In modern parlance this is known as the 82% zone and it is this "zone" that an observer would endeavor to "place" on the target through adjustment...

Here is an modern American reference that explains it in detail..... I think that it is important to remember that despite the modern age of the reference, the concept of PEs is old and the mention of PEs in 1944 (1951) refers to the same concept as today.

Some examples...

600 yds (from mortar to target) Ch 2 PEs are 10 yds for range and 6 yds for deflection. This gives a beaten zone (100% box) of 80 yds long and 64 yds wide with most of the rounds landing in a box 40 yds long and 32 yards wide.

200 yds (from mortar to target) Ch 0 - PEs are 5 yds for range and 2 yds for deflection. This gives a beaten zone (100% box) of 40 yds long and 16 yds wide with most of the rounds landing in a box 20 yds long by 8 yards wide.

Now this is a lot, I know, but with this data, we can say categorically if mortars are too accurate in this game.... Now all this data is based on real weapon performance but in perfect conditions with perfect aiming (laying). Battered sights, tired eyes, worn mortar tubes and the weather will all combine to give more error to the shooting.

Thanks for indulging me in my explanation and please ask any questions you like.

The references

For Theory of PEs - http://www.fas.org/man/dod-101/sys/land/docs/fm6-40-ch3.htm

For PE of the mortar - http://winslettwedding.com/FT%2060-L-1%20Firing%20Tables,%20Mortar,%20M19%20and%20M2.pdf

[akd]

Thank you for the actual firing tables.

[Steiner14]

@Rob Deans

great post.

So let's try to derive the hit probability of a single shot, or how many shots are necessary to hit a certain area:

If this book is correct (http://www.scribd.com/doc/73158902/Der-leichte-Granatwerfer-36), the hit probability for the l.Gr.W. 36 was calculated with a rule of thumb that way (page 8):

"Die Trefferwahrscheinlichkeit wurde nach einer einfachen Faustformel ermittelt: Zielausdehnung dividiert durch eine 50%-Streuung ergab die Treffwahrscheinlichkeit."

Hit probability = target (area) divided by 50%-dispersion (area).

Now using your great source Fig. 3-12 (http://www.fas.org/man/dod-101/sys/land/docs/fm6-40-ch3.htm) shows, that the 50%-dispersion area is achieved by using two of the center lines - either the two inner range columns or the two inner deflection rows

With your example

400 yards

range: 8 yards

bearing: 4 yards

This results for an area @400yards containing 50% of hits:

Area with the whole two inner bands in range (2x 4 yard bearing = 8 yard)

x the whole range (8x 8yards = 64 yards) = 8 x 64 yard² = 512 yard².

Calculating the area again but this time using the deflection band: 2x8 yard x 8x4 yard = 512 yard².

Ok, that seems to fit.

So we have an area of 512 yard² @400m in which 50% of all rounds will fall.

Now back to using the rule of thumb for the hit probability of the l.Gr.W. 36 p[%] = (target area) / (50%area)

Let's assume the size of the target, for example a HMG with 3yard x 3yard = 9 yard².

Then following this rule of thumb the hit probability would roughly be 9/512 = 1,8% or 57 rounds for one hit in the target area .

[YankeeDog]

Steiner -- That's fine, but your the target area you are using is way too small to draw any useful conclusions about how likely any given mortar shell is to land close enough to an MG to take the MG out of action (unless you're trying to figure out how likely it is that a shell will land close enough to the MG to actually blow the gun itself to bits). Hitting within a 3m x 3m area is not necessary to render an MG position combat ineffective with an 81mm mortar, or even a 60mm mortar for that matter.

50% lethal radius for a 60mm shell is considered to be about 15m. So a 60mm shell falling within 15m of an MG position will *usually* wound at least one, and often two, of a 3-man MG crew (gunner, loader, spotter) The lethality % drops off pretty quickly after 15m, but there is still a significant chance of wounding at least one crew member out to 25m or so.

Lethality radius for an 81mm bomb would obviously be a fair bit larger - on the order of 25-30m, IIRC.

Then following this rule of thumb the hit probability would roughly be 9/512 = 1,8% or 57 rounds for one hit in the target area .

Also, this is a false assumption. It's not an even distribution about the impact area. Rather, concentration of hits is tightest around the center, and falls off towards the edges -- as detailed in the dispersion chart you linked in your post. So you can't assume that the chances of a given shell falling within a 9m^2 area of the 512m^2 area is 1.7%. If the 9m^2 area is close to the center, it will be much higher. If near the edge, it will be much lower.

[YankeeDog]

In determining how close is "close enough" for light mortar fire, This section from FM 7-90 "Tactical Employment of Mortars", may be of use. This is a modern (1992) publication, but as I understand it, there have only been very modest improvements to the lethality radius of light mortar shells since WWII (most of the tech improvements to these weapons systems have been in range, targeting time, accuracy, and airburst (VT) fusing)

Quoted from here:

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

a. If a 60-mm mortar round lands within 20 meters of a target, the target will probably be suppressed, if not hit.

b. If a 60-mm mortar round lands within 35 meters of a target, there is a 50 percent chance it will be suppressed. Beyond 50 meters, little suppression takes place.

c. If an 81-mm mortar round lands within 30 meters of a target, the target will probably be suppressed, if not hit.

d. If an 81-mm mortar round lands within 75 meters of a target, there is a 50 percent chance that the target will be suppressed. Beyond 125 meters, little suppression takes place.