Mortarfire by mapcoordinates?

[Pak40]

Awesome, thanks for the insight and details.

[GreenAsJade]

I ran an 81mm mortar section in Vietnam for 10 months. I believe our equipment was similar to the WWII stuff. Here is the deal on grid fire.

When the mortar section is first located it must be "laid in", the gun base plates are settled, the aiming stakes are put out and the tubes are individually fired in to hit known spots. The slip scales on the sights are moved to agree with the FDC plotting board.

The plotting board in FDC was grease pencil marked with grid lines. In an actual fire mission the FO could call in a grid coordinate as a target along with the FO-Target magnetic compass direction. FDC marked the mortar location and the target location on the grid board. They then produced the tube sight data which was sent to the guns.

The reason you needed an FO to adjust the fire was because the first round usually wasn't on target. Why, because each time the guns had been fired since initial section lay, the base plates would usually move slightly. This fact screwed up the aiming stake-mortar-sight geometery and would produce a small error that grew until the section was re-laid. Other variables like humidity and ammo variables could make things worse.

So the FO watched or listened to the first round and called FDC with corrections. By rotating the plotting board wheel to the FO-Target direction as corrections came in, FDC could view the problem from the FOs perspective. They then marked the correction with a grease pencil on plotting board, rotated the plotting wheel back to grid North and sent new sight data to the guns. Once a round was on target the FO called for "Fire for Effect".

And good things happend.

Very interesting.

Given all this difficulty of hitting targets, how realistic is it that in-game, 81mm mortars can be walking through a field at one moment, and within not many seconds (30?) they can be landing rounds on some enemy position that they spot?

GaJ

[Crushingleeek]

really good stuff.

how large is the base plate on a 81mm? I'm sure it had to be a trade-off between stability and portability. just wondering

[Rafter11]

Very interesting.

Given all this difficulty of hitting targets, how realistic is it that in-game, 81mm mortars can be walking through a field at one moment, and within not many seconds (30?) they can be landing rounds on some enemy position that they spot?

GaJ

Well if the mortar crew can see the target, they can be pretty quick. No need for aiming circles or aiming sticks. If it was me, I would use the first round to set the baseplate. There is a card in each ammo box with recomended charges/tube elevations for range. 30 sec would be pretty quick for amatures. Veteran troops, maybe so.

[Rafter11]

really good stuff.

how large is the base plate on a 81mm? I'm sure it had to be a trade-off between stability and portability. just wondering

I was in the 101st and we had the airborne baseplate. It was lighter and smaller than the standard baseplate. I am going to guess it was 2.5 feet across. It has been 40 years, memories fade.

[Rafter11]

Awesome, thanks for the insight and details.

One point to consider is that the killing radius of a Vietnam era 81 round was 35 meters. A first correction of right 50 meters-add 50 meters for a first round was very rare. A more normal first round correction would be something like right 200 add 150. At the other extreme, if the correction ever came back around 500 meters, everybody involved would go, "whoa, something is not right".

So to think you could do some good with a blind fire on a gird square is, in my humble opinion, unrealistic.

[Pak40]

Since CMx2 engine was released, I've always wondered at the accuracy of a line artillery barrage. In your opinion, is it realistic for a mortar or 105mm battery to lay a line barrage with the kind of accuracy we're seeing in CMBN? It just seems like an awfully complicated thing to pull off.

[Bradley Dick]

Since CMx2 engine was released, I've always wondered at the accuracy of a line artillery barrage. In your opinion, is it realistic for a mortar or 105mm battery to lay a line barrage with the kind of accuracy we're seeing in CMBN? It just seems like an awfully complicated thing to pull off.

If we're just talking about artillery in general and not WWII specific, I can vouch for linear fire missions being fairly damned accurate. I watched 155 rounds walk down a street with barely a drunken swagger and I've heard rocket artillery crews ask which side of the house we wanted to hit with the rockets. Artillery has come a long way from cannons sitting atop wagon wheels.

[Crushingleeek]

Let me ask this Rafter11:

Do you think mortar/artillery is modeled just right/over-represented/under-represented in CMBN?

I know BF has put a ton of research/effort/thought into all aspects of CMBN, but any real-world input from veterans, Rafter or other ppl perusing these forums, could always be helpful.

I'm all for realism, even at the expense of gameplay. I just thought, like someone mentioned, that FO's could judge based on explosion clouds, not necessarily in their direct line of sight (a could of smoke behind a patch of trees in their LoS), how to direct fire.

[JonS]

I just thought, like someone mentioned, that FO's could judge based on explosion clouds, not necessarily in their direct line of sight (a could of smoke behind a patch of trees in their LoS), how to direct fire.

They can, and they do. But it isn't a panacea. One of the major problems FOs face is that they never really know exactly how far away something is. They can estimate, and they can read a map, but until you start firing rounds and SEEING where they land, you just don't know. That's why adjustments are done as a bracket - one over, one under, then progressively halve the interval until you're on the target (or, to put that more accurately, the footprint of the fire unit firing FFE is over the target area).

If you can see the target, and one of your adjusting rounds lands long in some trees, or behind some buildings, or even over a ridge; no problem. Even though you don't know where the round landed, you DO know that it was long of the target, and you can carry on adjusting based on that.

But firing at a target out of LOS, and adjusting based on plumes? You're just wasting everybody's time.

IMO, the speed, accuracy, and flexibility of indirect fire in CMBN is significantly over modeled compared to Reel Life WWII norms. However, in the context of the game - where everything goes much faster and more flexibly because of the God In The Sky, and the ability to order any unit to do almost anything almost instantly - it's about right.

[JonS]

I've always wondered at the accuracy of a line artillery barrage. In your opinion, is it realistic for a mortar or 105mm battery to lay a line barrage with the kind of accuracy we're seeing in CMBN?

The British had been practicing them since at least 1915, so, yeah; it's realistic. Certainly for artillery, although maybe not so much for battalion-level mortars with their more limited command post resources.

FWIW, you might want to set up a test - in the game there is usually a reasonably large dispersion on each side of the nominal line that the guns are firing along. The rounds don't fall in a perfect join-the-dots line, which is a good thing. Good because it's much more realistic that way, and good because that spread of rounds is good for you as a player, since it means that a larger total area gets hit well, rather than a thin line being over-hit.

It just seems like an awfully complicated thing to pull off.

It is, kinda, but it was certainly doable. However, like circular targets of various non-standard sizes, it took a while to calculate the individual bearings and elevations for each gun. Which is why, if I were to go ultra hardnuts, I'd recommend allowing any type of artillery mission during the setup phase, but only point targets once the game has started. Except that approach currently founders a bit because it's a challenge to put together a decent fireplan with the tools that currently available.

[womble]

I'm all for realism, even at the expense of gameplay. I just thought, like someone mentioned, that FO's could judge based on explosion clouds, not necessarily in their direct line of sight (a could of smoke behind a patch of trees in their LoS), how to direct fire.

Now you're talking (in re: the game) about the FOs being able to adjust fire based on splashes outside their "official" LOS, which they can do, or at least the spotting process continues to improve the zeroing in. Whether that's just a consequence of regression towards the mean (if the first random shot missed by miles and so was out of sight, the likelihood is that another randomly targetted spotting round will land closer) or whether the spotter algorithm actually can see shellbursts I couldn't say.

[Rafter11]

Since CMx2 engine was released, I've always wondered at the accuracy of a line artillery barrage. In your opinion, is it realistic for a mortar or 105mm battery to lay a line barrage with the kind of accuracy we're seeing in CMBN? It just seems like an awfully complicated thing to pull off.

Great Question! Keep in mind that a WWII era Mortar was an area weapon.

The short answer to your question is Yes, I think CMBN is fairly realistic on this matter and Yes a linear mission could be complicated. In the triple canope jungle mountains of Northern South Vietnam, nothing was square or linear, so I never once actually did a linear fire mission on purpose. We did learn to fire them at the Infantry School in Ft. Benning.

That said, when I laid in my three tube section, I made my impacts linear. The mortar tubes were numbered 1,2, and 3. from right to left. First I fired in the center tube, which was #2. Then we adjusted the 3 tube to impact 20 meters to the left of 2 and adjusted 1 tube to impact 20 meters to the right of 2 tube. Once we had that done, the slip scales on all three sights were set to the FDC/tube 2 firing data. If my line of mortars was running North and South and I was firing to the West during section lay in, I could expect a North/South linear impact pattern when engaging a target to my general West.

If the target was not located to my West or if the FO would have ever wanted a linear orientation other than North/South, the FDC had to plot each tube's data seperately. That would make things complicated and slower.

Since I would do all the Adjust Fire shots with the #2 tube, I would expect the most variance in the initial rounds fired from tubes 1 and 3. I am going to run a CMBN linear mission and pay attention to what happens with the right side and left side initial impacts.

I don't know much about 105s, however I heard one very well sourced story about a Marine FO protecting his escaping recon unit with a moving box of four sided linear missions fired from four different arty units. It is my understanding from reading WWII history that the Arty really put their pre-war time to good use and developed some amazing capabilities.

[Crushingleeek]

.....whoa....

[Sublime]

talk about pressure huh? four sided box of artillery means that you're always in the danger zone. Hope they bought that guy rounds for years..

rafter I was very intrigued in what you had to say - I'd love to hear anything and everything about your Vietnam experiences you'd like to share...

[Crushingleeek]

I don't know much about 105s, however I heard one very well sourced story about a Marine FO protecting his escaping recon unit with a moving box of four sided linear missions fired from four different arty units. It is my understanding from reading WWII history that the Arty really put their pre-war time to good use and developed some amazing capabilities.

Imagine trying to carry that out in CMBN.

if you hadn't said well-sourced, i'd put it in the folklore folder:D

[Rafter11]

Let me ask this Rafter11:

Do you think mortar/artillery is modeled just right/over-represented/under-represented in CMBN?

I know BF has put a ton of research/effort/thought into all aspects of CMBN, but any real-world input from veterans, Rafter or other ppl perusing these forums, could always be helpful.

I'm all for realism, even at the expense of gameplay. I just thought, like someone mentioned, that FO's could judge based on explosion clouds, not necessarily in their direct line of sight (a could of smoke behind a patch of trees in their LoS), how to direct fire.

If those are my choices, I would pick "just right". I think they have done a pretty good job mixing realism with gameplay.

For instance, CMBN has simplified and shortcut some of the FO tasks with respect to the TRPs. In real life, each TRP would have to be fired in and the firing data retained for future use. But who among us wants to spend all that time in a game setup.

The one complaint I have with the on board mortars is my inability to load a Duece and a Half with extra mortar ammo and drive it around behind the mortar section.

[Pak40]

The one complaint I have with the on board mortars is my inability to load a Duece and a Half with extra mortar ammo and drive it around behind the mortar section.

Yea, I think this is a game balancing issue. Theoretically a supply jeep or truck could keep on board mortars in constant supply so long as battalion and regimental supplies are plentiful. But, I suppose they have to draw the line somewhere.

[womble]

The one complaint I have with the on board mortars is my inability to load a Duece and a Half with extra mortar ammo and drive it around behind the mortar section.

There are mortar unit options that let you do that. My recollection is hazy, but the mortar sections in the support company of a tank battalion, on both sides, I think, comes with vehicles which have extra ammo, if you pick "on board" for their mode. The US ones are M7(?)/M20 halfies, but there is, I believe, a German option to have an Opel Blitz with reloads, though that might be in a different formation, with the tank Bttn having mortar half tracks.

[Seedorf81]

I ran an 81mm mortar section in Vietnam for 10 months. I believe our equipment was similar to the WWII stuff. Here is the deal on grid fire.

When the mortar section is first located it must be "laid in", the gun base plates are settled, the aiming stakes are put out and the tubes are individually fired in to hit known spots. The slip scales on the sights are moved to agree with the FDC plotting board.

The plotting board in FDC was grease pencil marked with grid lines. In an actual fire mission the FO could call in a grid coordinate as a target along with the FO-Target magnetic compass direction. FDC marked the mortar location and the target location on the grid board. They then produced the tube sight data which was sent to the guns.

The reason you needed an FO to adjust the fire was because the first round usually wasn't on target. Why, because each time the guns had been fired since initial section lay, the base plates would usually move slightly. This fact screwed up the aiming stake-mortar-sight geometery and would produce a small error that grew until the section was re-laid. Other variables like humidity and ammo variables could make things worse.

So the FO watched or listened to the first round and called FDC with corrections. By rotating the plotting board wheel to the FO-Target direction as corrections came in, FDC could view the problem from the FOs perspective. They then marked the correction with a grease pencil on plotting board, rotated the plotting wheel back to grid North and sent new sight data to the guns. Once a round was on target the FO called for "Fire for Effect".

And good things happend.

Sorry for late reaction, was working nightshift. This reaction, and the first one from Rockybalboa answered my question. I did overestimate the non-spotter WW2 artyaccuracy. Thanks for your replies, boys!

[Rafter11]

You can adjust fire by sound. It is less accurate and more dangerous. But when you can't see 20 meters because of the forest, you have to.

The BN S-3 is supposed to know where all the good guys are. We could not fire a mission without his approval initials. So someone was making sure you weren't starting a friendly fire incident.

Let's take the nightly TRPs for example, When I was an FO, the rifle platoon leader would come to me each evening when we were setting up camp and say, "I think we are here and I want DTs (TRPs) fired in here and here and here around the perimeter. First, you plotted them on your map and wrote down the grid coordinates. Since they were DTs, their locations could not be sent in the clear, they had to be encoded first. I then called in the coded grids for our location and the DTs to FDC. They decoded them and got S-3 Clearance initials, plotted the first DT and sent the data to the number 2 gun.

When the adjusting round was fired, FDC called me and said "Shot Out on your DTxxx, time of flight 36 seconds". Just before the round landed they called me and said "Splash 05".

Because I had plotted the DT on my map and I knew my location (sort of), I could connect the dots and get an OT line (Observer-Target) and compass bearing from the map.

While the shot was in the air, I would turn my body w/compass so I was looking right down the OT line and make sure my head was centered on my body. When the round impacted I could tell by sound if it was right or left of the target line. I had to guess the range and call in the correction. I was surprised how close we could get to the spot.