Greetings.
Manual Mortar operation for kids who want to mortar better.
We will be using the gunnery interface and a precalculated range table, not the artillery computer, because it is 1968 and computers are massive, like a whole room.
To access the gunnery interface, get in the mortar as a gunner and right-click to bring up the optics.
I recommend having pencil and paper handy, and a calculator can be helpful as well, or slide rule, I guess. It is 1968, what is a calculator?
M29 range table pdf
M2 60mm range table pdf
Operating the mortar interface
Essential mortar operation is placing indirect fire on a target at range.
To do this, you need to know four things.
Bearing to target
Elevation
Propellant "Charge."
Type of ammo
M29 interface image
The interface for each of these is pretty standard Arma stuff.
Bearing is by turning the tube left or right with the mouse.
Elevation is set with the "Page Up" and "Page Down" keys. Hold "Shift" for smaller increments.
Charge is set with "Next Weapon" key, typically "f."
Type of ammo set using the "action menu," usually the mouse wheel.
Bearing
The bearing is pretty simple. In the gunners' view, top of screen, center, red numbers. That is your bearing.
We would typically figure out the bearing with a compass.
Sometimes by direct observation, sometimes by using the compass on the map.
The bearing has to be from the mortar position or pretty close. The further away the compass bearing is read, the more error you introduce.
If the digital compass is enabled (shift + click on the map), you can mark your target with this and turn the mortar to that bearing. Having a bearing is faster.
Elevation
Here is where the range table (attached) comes in.
In its simplest form, elevation is directly related to range.
The rule for elevation changes
For walking fire you can turn the tube, as well as make small adjustments in the elevation. You will also be expected to make small corrections and fire for effect, so remember "Farther is lower (page down)".
A basic example
Let us say your target is at a range of 250m from your mortar position.
Using the range table, I see that 250m is in the close charge range, with an elevation of 74.98. Set your elevation and boom, rounds downrange, a flight time of about 14 seconds.
Calculating for a height difference
Now let us say your mortar position is up high on a hill, FSB Berchtesgaden in Cam Lao Nam in this case, and your target is down in a valley.
You can read height on the map using contour lines, or if enabled, the mouse pointer will show you a 6 figure grid reference and the height at that point.
The mortar height is 435m, the target is at 270m giving us a height difference of -165m.
Our data so far:
So we look it up in the range tables for 500m gives us:
Medium charge
meters ELEV DR time
500 82,72 0.17 28.3
The range table gives us a medium charge, with an elevation of 82.72 and DR of 0.17.
So for a 200m height difference, we multiply 0.17 by 2, giving us 0.34.
The mortar is above the target, so we add the offset to the elevation. (Do the opposite if the target is above) giving us 82.72 + 0.34, giving us 83.09, which is our completed firing solution with a flight time of about 28 seconds.
Charge
The charge determines the amount of propellant on the mortar round.
More charge means more flight. More flight means more range and flight time.
Generally, you will want the lowest possible charge for your desired range.
Some ballpark numbers for you.
charge 0 (close) : 100m to 450m, about 10 to 15 seconds flight time
charge 1 (medium) : 350m to 1850m, about 25 to 30 seconds flight time
charge 2 (far) : 700m to 3800m, about 35 to 40 seconds flight time
The charge is set using the "f" key by default.
Ammo Type
Ammo types are pretty self-explanatory.
Type of round is set using the action menu (mouse wheel):
HE: high explosive (boom)
WP: white phosphorus (burn)
LUME: Illumination flares (light)
Smoke: smoke (smoke)
Placing rounds on target
You can approach this in a few different ways, depending on the situation.
Map Reference
On contact with the enemy, someone places a mark on the map.
The gunner then figures out the bearing, range, elevation, and height difference, if there is any.
Set bearing, set charge and elevation, rounds out.
Bearing and Range
The gunner is provided with the bearing and range to the target directly.
All that is required is a range table lookup, and we can send rounds.
This can be a rapid response once players are working in concert.
Pre-plotted Range Card
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Upon establishing a mortar position, make some observations or landmarks around the position or expected enemy positions.
Create a list of identifiers for these marked positions and work out the required bearings and elevations in advance.
Players can then call out enemy contact in reference to these positions, and the gunner can respond with accurate fire rapidly.
On the Mike Force TFAR servers the "TRP number" references serve this role.
The range card information can be handled on paper by the gunner.
Appendix A: Calculating map distance
Using the standard 6 figure grid reference in the arma map, we can calculate the distance between any two points.
Note: Using this approach, you may notice a discrepancy with the digital compass if you measure points at different heights. This formula does not account for height at all, where the digital compass seems to measure distance like a beam from point to point. This height discrepancy with the digital compass can introduce errors when you calculate height offsets for mortar elevation.
dx = xpos(target) - xpos(mortar)
dy = ypos(target) - ypos(mortar)
sqrt(dx2 + dy2)
ans * 100 = map distance in meters
Using an 8 figure grid reference in the arma map does the same steps but only multiply by 10 to get the meters.
dx = xpos(target) - xpos(mortar)
dy = ypos(target) - ypos(mortar)
sqrt(dx2 + dy2)
ans * 10 = map distance in meters
For example
Let us say you are at 140 160 right on the gridlines.
Your x is 140, and your y is 160
Your target is 130 170, also right on the gridlines.
Their x is 130, their y is 170
I find a handy way to do this on paper is to deal with them as two columns.
Work them as an X column and a Y column.
T 130 170
M - 140 - 160
dx = -10 dy = 10
-10^2 10^2
100 100
sqrt(100 + 100) = 14.14
14.14 * 100 = 1414 meters
Quick howto on 8 figure grid references
To get more accurate, you can use an 8 figure grid reference where you break down each grid by another ten units.
- X first, left to right
- Y next, bottom to top
Dead center in 135 221 would be written as 1355 2215 for example
Shoutouts
Just wanted to thank Pleb and Foster and the crew of Mike Force #6 for putting up with some mad science tonight as I worked though some of the process and math for this document.