How is a mortar aimed?


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Tokugawa
July 22, 2007, 12:51 AM
How is an indirect fire weapon like a mortar aimed? If the shooter and target are hidden in dead ground, you would need a spotter, yes? Is this all done with "old" tech, or do we use a lazer rangefinder and direction (compass point) finder coupled with a gps to establish the target coordinates and transmit to shooter/ I.E.- the spotter know his gps position, shooters gps position, and distance and angle to target, and computer figures targets gps position, and direction and trajectory from the shooter?

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bogie
July 22, 2007, 01:08 AM
It's usually aimed very carefully, sometimes due to directions being given by a 2nd Lt. who is carrying both a compass and a map.

Ron James
July 22, 2007, 01:13 AM
And being a Retired CSM, I can tell you for a fact, both the mortar and the 2nd LT. with a map, are equally dangerous. :)

Alphazulu6
July 22, 2007, 01:18 AM
It's usually aimed very carefully, sometimes due to directions being given by a 2nd Lt. who is carrying both a compass and a map.


I hope the PSG is standing nearby..... HAHA

Ok seriously not to bash a 2LT (I know how it feels to be one) A mortar is aimed using a "sight" that is set up for Mils (not degrees). It is really not all that hard just that the trajectory, elevation, windage, type of target all have to be determined. And a good E-6 mortar section sergeant will take care of that!

rangerruck
July 22, 2007, 03:15 AM
you could use a spotter, but that is not 100 percent necessary. if you can read a map, and have a target you wish to acquire, you can do it, but you still would need someone, with a pair of binos, with you , at a minimum, from your position, to see if you have hit your target. if you are say, close enough with a first or second shot, or even a third, you can then fire for effect, rain down the rest of your ammo on that spot, and if you have other mortars, in you platoon or company, they just light up the same area you are shooting into.

Jdude
July 22, 2007, 04:41 AM
2Lts are not to be trusted with a map. Ever.

As to the mortar: Usually it is a Spc. (army) or LCpl (marines) with a chart of known ballistic flightpaths. That soldier selects the approriate flightpath for his chosen range and time of flight, points the tube accordingly, and after an okay from his superiors, lets one go.

Jubjub
July 22, 2007, 06:30 AM
They have an optical sight that is attached to the gun. If the target is in sight (rare for mortar fire) they can aim directly at it. More commonly, they sight on an aiming stake placed in the ground 50 or 100 meters from the mortar, and just use the sight as a reference.

Hank Zudd
July 22, 2007, 08:40 AM
Practice.

Don't know about all mortars, but some are hastily setup & fired as mostly described above. However with larger calibers, you need a fire direction controller to use some trig to determine the guns position relative to the target. I shot 155's & it takes a little time (couple hours) to setup an accurate battery. "Spotters" are commonly called forward observers; they direct the fire adjustment relative to the target & where the first shot hit. I shot 100's of rounds & never saw where they hit; that's the FO's job.:uhoh:

Smith357
July 22, 2007, 08:53 AM
First sighting posts are set out at a known compass heading. From there coordinates for a fire mission are calculated by the FDC (fire direction control) and settings are relayed to the gunner who puts the settings in the sight and then lines the gun back up on the sighting posts as the ammo men adjust the charge level on the rounds for distance from 1 to 9 increments. Then a single round is dropped down the tube. A forward observer will relay back to the FDC if any adjustments are needed and then they fire for effect. Typical setup time from the mortar being in pieces to dropping the first spotter down the tube is about 3 minutes. Setting the aiming posts takes the most amount of time.

AK103K
July 22, 2007, 09:19 AM
How is a mortar aimed?
Trying to find the "Green Zone" are we? :)

daniel (australia)
July 22, 2007, 09:30 AM
First sighting posts are set out at a known compass heading. From there coordinates for a fire mission are calculated by the FDC (fire direction control) and settings are relayed to the gunner who puts the settings in the sight and then lines the gun back up on the sighting posts as the ammo men adjust the charge level on the rounds for distance from 1 to 9 increments. Then a single round is dropped down the tube. A forward observer will relay back to the FDC if any adjustments are needed and then they fire for effect. Typical setup time from the mortar being in pieces to dropping the first spotter down the tube is about 3 minutes. Setting the aiming posts takes the most amount of time.

That is fairly much how I remember it too. Your mortar team first plants the baseplate into the ground, sets up the mortar and attaches the sight unit, which has two spirit levels to get the sight level front-to-rear and side-to side. The sighting posts are like what surveyors use, and usually one is set out at a convenient distance in front of each tube and one 180 degrees behind the tube. They are set out carefully using a compass. Actually one would be enough, but the second is there as back-up in case the first is damaged by fire etc.

When the "2lt with the radio" calls in the fire mission it is received by a mortar fire controller, who has a plotting board over a map showing, amongst other things, where the tubes are and where the fire mission is being called in from. Unless the target has already been ranged, the MFC calculates where the fire is to strike, usually by translating the bearing and range from the bloke with the radio into a bearing and range from the tubes, using the plotting board. He then calculates the charge and elevation necessary to reach that range.

The charge and projectile are called to the mortar crew/s, and then the bearing and elevation. The mortar No. 1 sets the sight unit to that bearing and elevation, and then adjusts the tube so that the two bubbles are centred again and the crosshairs of the sight are lined up on the aiming post - giving the elevation and bearing respectively, while the No. 3 prepares the rounds with the right charge. At that point all is prepared (if the 2lt hasn't stuffed it all up) for the bringing of bad news to the bad guys away over there.

BTW all of this, with a good crew, should take only a few short minutes from the tubes being on a vehicle to giving the nervy guy on the radio "shot over".

Cannonball888
July 22, 2007, 10:30 AM
First, you need a crew of 5 people just to load the shell, then you need a half dozen officers to direct the fire :D

http://www.iphotocentral.com/Photos/VintageWorks_Images/Full/1393CivilWar.JPG

GRIZ22
July 22, 2007, 10:50 AM
I shot 155's & it takes a little time (couple hours) to setup an accurate battery.

That is really slow and wouldn't get you out of gun bunny school at Fort Sill.

If a mortar or artillery piece is set up and has time to register (shoot at a known location) where the fire is adjusted visually everything else is shooting from a known point and is very accurate unobserved fire.

Unobserved fire is avoided if possible as all the variables can put you off target and shooting dirt has no effect on the enemy.

Aguila Blanca
July 22, 2007, 12:58 PM
I shot 155's ...
That must be a VERY large mortar.

brickeyee
July 22, 2007, 01:03 PM
Just above 6 inches.
http://www.g2mil.com/155mortars.htm

Hank Zudd
July 22, 2007, 05:00 PM
Griz22- from the time the advanced party occupies a firing point, lays out a point for each gun, gun crews roll in & set aiming stakes, checks backsight to FDC, sets gun ready, set cammo netting (15 min for all these task) it's at least an hour. Course doctrine has changed since early 90's when I was doing this. (Pallin was just comming online) Your right, to occupy a spot & get rounds down range needs to be quick. I only had a year in the unit till I went back to flying, so I never had the chance to occupy a "virgin" firing point. We did do one fire mission, hand ramming 3 rounds in 45 seconds. Of course we're talking about SP arty, not mortars. Mech infrantry divisions have tack mounted 120's.

GRIZ22
July 22, 2007, 05:20 PM
Griz22- from the time the advanced party occupies a firing point, lays out a point for each gun, gun crews roll in & set aiming stakes, checks backsight to FDC, sets gun ready, set cammo netting (15 min for all these task) it's at least an hour. Course doctrine has changed since early 90's when I was doing this.

OK Hank when you throw all this in I'll agree with that time. I think the ARTEP standard in the late 80s was something like 15 min for a hipshoot. 3 rds in 45 sec with a towed 155 is great time. We put out a round every 40-45 seconds with an 8" in Vietnam for awhile. Yes I know that exceeds sustained rate of fire but sometimes you don't worry about such things.

I apologize if I offended you. Nice to see guys here who have shot something bigger that a 50 cal.

Langenator
July 22, 2007, 06:10 PM
Current mortar calibers in the US inventory: 60mm, 81mm, 120mm. There may also be 4.2" (107mm) mortars left in some NG mechanized units.

Current artlillery calibers in use: 105mm, 155mm. The 8"/203mm was phased out in favor of the MLRS (227mm rockets)

daniel (australia)
July 22, 2007, 08:27 PM
I probably should add to my post that once you've set up and got the first round out to where the bloke with the radio wanted it it is of course usually necessary for the rounds to be "adjusted" onto the target, using instructions from the bloke who called it in. The mortar crews usually can't see the target and don't need to (which is why it is called "indirect fire").

The trick to this is that the bloke observing the fall of shot gives adjustments based on his point of view, and these must be converted by the plotter into adjustments from the point of reference of the mortar crew. To do this the plotter again needs to know the position of the observer, and the bearing from the observer to the target. Thus when the observer says "add 100" the plotter recognises that this means "move the fire 100m further in the direction between me and where I said the target is".

The correction from the point of view of the mortar location may be quite different - for example the observer may be facing 90 degrees to the line between the tubes and the target and thus the observer's "add 100" may require an adjustment to the left from the point of view of the mortar crews.The plotter makes this calculation for the crews, and they adjust according to his instruction.

With each adjustment a round is fired until the fire is on the mark, and then the full complement - "fire for effect" - is let go.

I hope I've explained that right. It was a long time ago, and I only did the mortars course so that I'd have a better idea what I was doing when I was out there with my radio, compass and map ;) .

Acera
July 22, 2007, 09:13 PM
The best manual for this and a lot of different questions is STP-31-18B34. Sometimes you will find it a gun show, or google it. Subject areas 1-8 will give you more information about mortars than you will probably want.

James T Thomas
July 23, 2007, 03:58 PM
A mortar is "aimed" by the combination of elevation; angle to the ground -horizontal, and azimuth; the traverse adjustment -side to side.

The aiming stakes are the reference. When the closer one obscures the farther one in your sight optics, then you are aligned.

My unit had to elevate our M29; 81 mm cannon or "tube" almost to the vertical of 1600 mils= 90 deg. Our setting was 1500 mils, i.e. 85 deg.
The tube had coarse threads on the outside which engaged the collar; that was supported by a bipod legs.
Fine adjusting was done by turning a crank mechanism; fine threads. It could be disconnected to make large settings. Both in elv. and traverse.
I believe it was 90 mils traverse available either left or right of center.

The gunner became very proficient at rapid and accurate cranking. He knew from experience, and training, how many cranks to get how many mils -I forget now. Depends on the number of threads.

My unit accompanied the rifle platoons out in the field one hot day. We were almost at the range limit of our artillery. We had to erect and set our single mortar (we had three) in an open field of gravel hardpan clay. No digging in for defilade cover! My gunner; Sgt. Charles White of Wash.D.C. manned that sight and made his adjustments under intense fire (three 12.7 mm Russian guns) and we brought fire upon the enemy as close as 80 m from us.
A burst from the M375 high explosive round had a killing area almost half of that distance, so it was close. But we needed it. We were unable to get our supporting artillery, but did obtain air power later on in the day. Sgt. White lived that day. A brave man. Some of the incoming rounds actually pinged off off that tube!

We could not set up the aiming stakes so the direction was simply swung to the position of the platoons to our front. They were close enough to observe if you would risk it and get up on your knees.
Adjustments were by radio communication until they were all (six) destroyed by snipers or the 12.7 guns. Mine was the last one, but we had already fired up the two dozen or so rounds we had been humping that day.

At the call for fire, we got the first round out in less than two minutes, though I did not time it.

That is how you expediently aim a mortar.

Gentlemen: Unless you have experienced this type of thing first hand, please refrain from the officer bashing. If you have "been there," you will know what it means to have that responsability.

41magsnub
July 23, 2007, 04:00 PM
The movie Stripes provides an excellent example of how to use a mortar.

Vern Humphrey
July 23, 2007, 04:12 PM
A mortar is aimed with a variation of a panoramic telescope sight. The sight has a rotating head with hash marks for mils (6400 mils to a circle) and a tilting feature with markings and level tubes (like a carpenter's level.)

The sight is "boresighted" to the mortar using a strap-on V-block elbow sight device. The V-block ensures the elbow sight is centered on the tube, and witness marks ensure it is on the same center as the panoramic telescope. The two sights are trained on a sighting board a fixed distance away, so the lines of sight for the panoramic signg and elbow sight are parallel.

The mortar is laid for direction using either an M2 compass or an aiming circle. If the latter is used, it is set up and aligned like a surveying device, and the mortar is "referred" back, adjusting the sight until both the Aiming Circle and the Pan-Tel sight read the same.

Then the sight is placed on standard lay and aiming stakes put out -- the gunner looks through the sight and directs his assistant gunner in placing out two stakes.

When a target is detected, firing data is calculated using a computer, firing tables or plotting board. Based on the range, direction (and sometimes altitude) of the target, the deflection (angle to set on the sight), elevation and charge are determined. The deflection is set on the sight and the mortar cranked around until the crosshairs of the sight are back on the aiming stakes. The elevation is set on the sight and the mortar cranked up or down until the bubbles in the levels are centered.

Depending on how the target was located, the mortar may fire for effect, or the observer may adjust fire. If the latter technique is used, the observer "splits a bracket" -- getting hits over and short of the target. The final bracket may be either 100 meters (for 120mm mortars) or 50 meters for 81 and 60mm mortars.

afsenior
July 23, 2007, 04:57 PM
I know !!!

I learned several years ago when antelope hunting in Wyoming with a 45-70...

Art

U.S.SFC_RET
July 23, 2007, 07:32 PM
Armies should fear accurate mortar fire, if they don't they quickly will if they ever face them in combat. A good crew can really put the fear of god on you hastily quick. They are calculated for a lot of damage.

hank327
July 23, 2007, 09:35 PM
Mr. Humphrey has it right. I was an 11C for four years in a line company using 81 mm mortars. We usually laid the section in using an aiming circle, which is basically a surveyors instrument. An M2 compass could be used to lay the guns, but that was not the preferred method. Once the guns were laid in, the sights were set to 2800 mils in deflection and 1100 mils in elevation and the two aiming posts were set out.

The aiming posts were used as a reference point for the sight. The posts were set out in such away as to appear as only one post when the sight was
referred deflection and elevation settings of 2800 and 1100. Before setting out the aiming posts, the gun is both level in deflection and elevation according to the spirit levels on the sight. When a fire mission is called, the FDC takes the information provided by the forward observers and translates it to fire command to the guns. The fire command goes like this.

FDC: "SECTION!"
The Section (aka the guns) repeats all the commands back to the FDC. Everbody yells: "SECTION!"

FDC: DEFLECTION...3210!
Section repeats : DEFLECTION...3210

FDC: ELEVATION... 1255
Section repeats: ELEVATION...1255

1 round HE QUICK, CHARGE 7

The gunners then dial the deflection and elevation settings onto the sight. Only the sight moves, not the gun.
Once the sight has the proper settings on it, the gunners then must physically move the mortar back to the aiming posts. If it is only a small shift, then you can make the adjustment with the traversing and elevation mechanism on the bipod. If it is a large shift, then the whole gun must be picked up and shifted. The assistant gunner will get down on his knees in front of the gun and with a hand on each bipod leg, lift the bipod up just enough to clear the ground. The gunner while looking through the sight with his left hand on the traversing handle and his right hand holding the gun tube at the muzzle then moves the mortar until the sight is back onto the aim posts. The gun is then releveled for deflection and elevation and then minor adjustments are made with the T&E mechanism with more releveling until the vertical crosshair of the sight is back in its proper position in relation to the aiming posts.

One note of interest. When a mortar makes a large deflection shift and the sight is brought back to the aiming posts, the aim posts will no longer be perfectly aligned on behind the other. You will now have two aiming post in your sights field of vision. what you do then is lay the gun in such away that the vertical cross hair is equal distant from the farthest aiming post as the farthest aim post is from the closest aim posts. That sight picture looks something like this: l l l

In mortar gunnery the horizontal crosshair is not used, only the vertical. When the gun is properly laid onto the aiming posts, the vertical cross hair is aligned along the lefthand edge of the aimposts.

Once the guns are laid on the firing coordinates, then the #2 gun (mortar sections have three mortars and the #2 gun is the center gun) fires the adjusting round. All the guns in the section follow the FDC commands, but only the #2 gun fires until the fire is adjusted onto the target. Once that occurs, the FO (forward observer) will tell the FDC to "Fire For Effect".

The FDC will then relay the command of "Fire For Effect" to the guns along with the number of rounds to be fired. After each round is fired, the guns are relaid upon the aiming posts. In my section, the gunner kept his eye on the sight as the rounds were fired and made the adjustments quickly. Once the baseplate is settled in, it only takes a minor twist of the T&E mechanisms to relevel the gun.

It takes a lot of teamwork and practice to be a good mortar section. But you can bring alot of steel on target in an amazingly short period of time if you have a well practiced crew.

A disclaimer: The last time I fired a fire mission was in the spring of 1982. There was no such things as GPS or electronic computers. What we called computers were men with M16 plotting boards and firing tables physically computing the FO's call for fire into commands for the guns. I heard of a couple of section sergeants buying the then brand new Texas Insturments programmable calculators with their own money to use in the FDC but I never saw one.

RocketMan
July 23, 2007, 10:27 PM
And they don't go "toonk" like you hear in the movies. Eighty-ones are loud! I've got the tinitus to prove it.
Sixties aren't far behind in sound level.

Sonora Rebel
July 23, 2007, 10:42 PM
During the Bosnian war... there was apparently a Mercenary 'sniper' mortar crew workin' for the Serbs. One guy with a GPS would enter the target area 'n record the position. He'd then call that in to a crew who were somewhere within' a wrecked house (with a hole in the roof) 'n they'd shoot 'n scoot. The round would land dead on target everytime. 60mm I think. Apparently they covered thei act by masquerading as 'movers'... hiding the tube in a rolled carpet 'n the base plate in some piece of furniture or behind a large mirror. They never got counter-whacked. (Possibly Russians) Whatever... they were really good at it.

Neo-Luddite
July 23, 2007, 10:53 PM
Hank327--that was a very nice and detailed response. I was going to be smart alec and just say--physics.

Tokugawa
August 12, 2007, 03:35 PM
Thanks for the responses, guys. For all those who have replied from experience, thank you for your service. Mr. Thomas, setting up a mortar in an flat open field covered by three heavy machine guns has to be about the least desirable thing to do I have ever heard of. The rest of your comrades must have been under extreme duress to require such an action. I am sure you have their eternal gratitude.

James T Thomas
August 13, 2007, 07:30 PM
Thanks Togugawa for not voicing skepticism about such an implauseable "war story."

If you are interested, some of the details can be read at Military.com>articles>Vietnam>"No DEROS Delta," by Steve Banko III.
You will have to register and accept their electronic cookies of course.

Ironically, the unit was 2/7 Cavalry, First Air Cav.Div; the same designation as Gen. Custer's. We wern't completely annihilated, but the enemy did try all the hot afternoon. The only cover we had was some high grass that caught fire from the munitions and added to our grief, and small mound anthills, perhaps eight inches in height that you could crawl around as you were persued by the snipers and big guns. One of them kept me from receiving a fatal neck wound by absorbing just enough kinetic energy to limit penetration to a little more than an inch from a sniper round.

The detail was taken from an after battle report, and is mostly correct, except that it states the 81mm tube was struck with a 12.7 mm round and destroyed. It was actually struck by an RPG round right at the moment when the gunner, assistants, etc. had dived away from the tube after firing our last round of ammunition that we had. I know because I remember the heat and blast and vibration from that, and saw the tube, baseplate, bipod and all flip through the air over my head.

It was a good "ambush" from the enemy's perspective, and the bravery of those who fought there will be remembered forever by the survivors.

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