105 Light Gun - Short Range Fire

De Bhál

so to start i know nothing about artillery equipment etc...zilch
Also I hope this is the correct forum.

I was in Smithfield yesterday and the Army had some equipment on display such as these guns and i was wondering about something...(remember I'm completely green to all this and couldn't find an adequate answer online elsewhere)





I see the maximum range is 17.2km. I have an idea how that works.
Now in a scenario where you've to fire say...3km and your sight to the target is blocked by a forest so you can't aim the gun directly at the target. Do you tilt the barrel up in the air at an extreme angle and lessen the charge or something or how do you fire on short range targets you can't see?

BoJack Horseman

I could be way off.... but I thought there was adjustable fuses/propellants in howitzers to adjust the range?
In that it is not just down to the angle of fire?

De Bhál

BoJack Horseman wrote: »

I could be way off.... but I thought there was adjustable fuses/propellants in howitzers to adjust the range?
In that it is not just down to the angle of fire?

I did a bit more searching using your added bit of info and yeah you seem to be right, it's down to the propellant. So I'm assuming the shells must be all different for different ranges or they're all the same and differing propellants are attached to them prior to firing.

From Wiki
The 105 mm Fd Mk 2 ammunition has two propelling cartridges and a blank cartridge (for saluting purposes). The normal cartridge has six propellant increments (charges one, two, three and four) plus 4½ and 5 increments. Charge 4½, which is charge five with the blue charge three bag removed, is only used for high angle fire. It is peculiar to the light gun. A separate "charge super" cartridge is used for firing to maximum range.

So I guess that by using the different propellants and adjusting the angle of the gun you achieve your target.

discus

Correct. It's called "High Angle". When the 105mm is firing at a close target, it will elevate the barrel at a pretty steep (near vertical) angle. There are rules for firing on high angle, such as adding spoilers to the shells.

De Bhál

ok, thank you.

found this using your info...
maybe useful for the unknowledgeable like myself

From the website
http://www.vietvet.org/arty.htm
HIGH ANGLE FIRE: artillery trajectory wherein the shell travels higher than its distance down range. Used for firing over intervening mountains, etc, inherently less accurate than low angle fire (standard) due to shell ballistics and wind effects.

riffmongous

I have a few questions actually, how are wind and air pressure corrections made? In the Irish case where does the met data comes from? I have a small book on the NVA (the german one) vehicles and they show a few mobile weather station trucks that they used found a link

John_D80

discus wrote: »

Correct. It's called "High Angle". When the 105mm is firing at a close target, it will elevate the barrel at a pretty steep (near vertical) angle. There are rules for firing on high angle, such as adding spoilers to the shells.

Had originally said that you were incorrect here but I misread your post!!

The high angle capability is generally only used in order to engage targets when crest clearance is an issue. Or where the target is right behind an obstruction as the OP was asking about. Short ranges (in 99% of cases) are far more easily achieved in low angle (less than 800 mils elevation) than high angle.

High angle (over 800 mils elevation) is both time and labour intensive because it takes a lot more effort to move the gun in this position. Accuracy is also greatly compromised. In high angle, targets can be engaged at both short and long range (within reason).

Short ranges (even as short as a few hundred metres) and long ranges alike are achieved by using different charges at various elevations.

John_D80

riffmongous wrote: »

I have a few questions actually, how are wind and air pressure corrections made? In the Irish case where does the met data comes from? I have a small book on the NVA (the german one) vehicles and they show a few mobile weather station trucks that they used found a link

Prior to and every 2-4 hours during firing, a weather (meteorological) ballon is released. This has a transmitter attached that sends the met data back to the gun battery as it passes through different levels of the atmosphere. The data is sent in what is known as a met telegram.

This data is then entered into the fire control system in the command post and appropriate corrections are applied by default to each round fired by each individual gun.

Victor

John_D80 wrote: »

less than 800 miles elevation

Mils?

https://en.wikipedia.org/wiki/Angular_mil

John_D80

Victor wrote: »

Mils?

https://en.wikipedia.org/wiki/Angular_mil

Obviously, but thanks for pointing it out. Corrected now. Could have been confusing. Lol

De Bhál

Thanks all for the info

Another question - you see in the photo I posted from Smithfield in the first post, there are these steel/aluminium rods (partly covered in a camouflage material) one either side of the barrel where it meets the supporting body. Now when I saw these I thought the were guns but on closer inspection I reckoned not. Are they for working out angles of tilt or something for the barrell?

John_D80

De Bhál wrote: »

Thanks all for the info

Another question - you see in the photo I posted from Smithfield in the first post, there are these steel/aluminium rods (partly covered in a camouflage material) one either side of the barrel where it meets the supporting body. Now when I saw these I thought the were guns but on closer inspection I reckoned not. Are they for working out angles of tilt or something for the barrell?

The rods are buffer rods and the camoflauge covers are concealing buffer springs. The buffers work with the hydraulic system to ensure the barell returns to its original position after firing and all elements of the firing mechanism are properly aligned once more.

discus

Had originally said that you were incorrect here but I misread your post!!

When I read your post I wrote a rebuttal but didn't post it because to be fair, I had left a lot out! I neglected all that good stuff on cresting etc. Also, it makes sense for HA to have less accuracy but I've never heard the FSTs call in corrections for HA that were any greater than those for Low Angle.

John_D80

discus wrote: »

I've never heard the FSTs call in corrections for HA that were any greater than those for Low Angle.

Without assuming anything may I ask where in the world you have fired the 105??

If it's in Ireland then the accuracy wouldn't be hugely compromised as we would only be firing high angle at VERY VERY short ranges. To the best of my memory, the max range for firing high angle in the Glen of Imaal is about 2.6km from one of only two or three gun positions where it is even allowed.

riffmongous

John_D80 wrote: »

Prior to and every 2-4 hours during firing, a weather (meteorological) ballon is released. This has a transmitter attached that sends the met data back to the gun battery as it passes through different levels of the atmosphere. The data is sent in what is known as a met telegram.

This data is then entered into the fire control system in the command post and appropriate corrections are applied by default to each round fired by each individual gun.

So the DF have their own radiosondes, interesting. And who takes care of it and the data? Internal specialists and who are they trained by? Cheers!

John_D80

riffmongous wrote: »

So the DF have their own radiosondes, interesting. And who takes care of it and the data? Internal specialists and who are they trained by? Cheers!

Sorry but I don't know what a radioSonde is!! :-)

All I know is that we have the balloons and they work!! I know also that they are very straight forward and user friendly pieces of kit. Never used one myself but have been very close (physically for observation purposes) to all phases of the process on more than one occasion. Most recently being about 2 years ago and I doubt much has changed in the interim.

discus

John_D80 wrote: »

Without assuming anything may I ask where in the world you have fired the 105??

UK, Norway, California and Jordan. Although I was manning a gun in Norway rather than the CP so I wasn't aware of the corrections involved for the high angle shoot.... That shoot was literally the best thing I ever did in a gunnery exercise.

John_D80

discus wrote: »

UK, Norway, California and Jordan. Although I was manning a gun in Norway rather than the CP so I wasn't aware of the corrections involved for the high angle shoot.... That shoot was literally the best thing I ever did in a gunnery exercise.

Wow you must have fired at or close to max range at some stage!!

Very jealous!!

riffmongous

John_D80 wrote: »

Sorry but I don't know what a radioSonde is!! :-)

All I know is that we have the balloons and they work!! I know also that they are very straight forward and user friendly pieces of kit. Never used one myself but have been very close (physically for observation purposes) to all phases of the process on more than one occasion. Most recently being about 2 years ago and I doubt much has changed in the interim.

Ah it's just the name for what you describe if I understood correctly (the box attached to the balloon). I've worked with them before for meteorology work, so I'm just curious to know if there is a cooperation between the DF and met eireann or if the army does everything independently

John_D80

riffmongous wrote: »

Ah it's just the name for what you describe if I understood correctly (the box attached to the balloon). I've worked with them before for meteorology work, so I'm just curious to know if there is a cooperation between the DF and met eireann or if the army does everything independently

I would be confident enough to say that the army does all of its own met analysis when it comes to firing artillery. The set up, launching of the balloon and input of data is fairly simple and only takes about 20-30 minutes by experienced operators and it would all happen as part of concurrent activity.

To be honest, at the ranges we are limited to in this country, we don't really need to apply met data at all but it's done as its good practice. When met balloons are not or cannot be used we would carry out what it's known as a registration mission, which basically is a means of firing a few rounds and finding out if and by how much we would need to ''aim off'' to account for weather conditions.

riffmongous

John_D80 wrote: »

I would be confident enough to say that the army does all of its own met analysis when it comes to firing artillery. The set up, launching of the balloon and input of data is fairly simple and only takes about 20-30 minutes by experienced operators and it would all happen as part of concurrent activity.

To be honest, at the ranges we are limited to in this country, we don't really need to apply met data at all but it's done as its good practice. When met balloons are not or cannot be used we would carry out what it's known as a registration mission, which basically is a means of firing a few rounds and finding out if and by how much we would need to ''aim off'' to account for weather conditions.

Yeah I guess there wouldn't need to be any cooperation at that level. Haha just making sure incase there would be a chance of a job down the line One of my old colleagues worked with the Bundeswehr in generating weather conditions for wargames or something, she couldn't tell me too much about it.

What level of accuracy would you be able to achieve in calm conditions and with all the data? Say to within how many metres of the target can you get consistently?

John_D80

riffmongous wrote: »

What level of accuracy would you be able to achieve in calm conditions and with all the data? Say to within how many metres of the target can you get consistently?

Careful mate or you will end up like Alice falling down the rabbit hole that is The Theory of Indirect Fire Support!!

Joking aside though, its impossible to give a reliable answer to your question as there are so many other variables besides Meteorilogical Data to consider:

-The degree and accuracy of geographical survey, orientation and fixation carried out by the fire unit.
-The accuracy of maps being used
-The types of weapons being fired
-The muzzle velocities of individual weapons
-The type of target and the effect required. Some targets would only need you to be within a hundred metres, others need you to be bang on
-The charge, nature and types of Ammunition and Fuzes being fired
-Human factors like setting of sights, calibration of instruments and application of data on to instruments and weapons.
-What we would consider as accurate changes dramatically depending on the range to the target.



Its like baking a cake. You dont just need to know the ingredients, you also need to know the amounts of those ingredients and the method in which they are mixed. You also need to know which ingredients you can leave out if nessecary and still be able to come up with a half decent cake.

Met data is probably a ''nice to have'' but not an ''absolutely must have''.

Getting accurate fire on the ground requires a lot of very skilled people doing a lot of very diverse technical work, sometimes under difficult conditions.

riffmongous

John_D80 wrote: »

Careful mate or you will end up like Alice falling down the rabbit hole that is The Theory of Indirect Fire Support!!

Joking aside though, its impossible to give a reliable answer to your question as there are so many other variables besides Meteorilogical Data to consider:

-The degree and accuracy of geographical survey, orientation and fixation carried out by the fire unit.
-The accuracy of maps being used
-The types of weapons being fired
-The muzzle velocities of individual weapons
-The type of target and the effect required. Some targets would only need you to be within a hundred metres, others need you to be bang on
-The charge, nature and types of Ammunition and Fuzes being fired
-Human factors like setting of sights, calibration of instruments and application of data on to instruments and weapons.
-What we would consider as accurate changes dramatically depending on the range to the target.



Its like baking a cake. You dont just need to know the ingredients, you also need to know the amounts of those ingredients and the method in which they are mixed. You also need to know which ingredients you can leave out if nessecary and still be able to come up with a half decent cake.

Met data is probably a ''nice to have'' but not an ''absolutely must have''.

Getting accurate fire on the ground requires a lot of very skilled people doing a lot of very diverse technical work, sometimes under difficult conditions.

It sounds very much like science/engineering really, can anyone train up to be one of the guys making the calculations or are people with a certain aptitude picked out in the beginning?

Thanks for all the answers btw!

John_D80

riffmongous wrote: »

It sounds very much like science/engineering really, can anyone train up to be one of the guys making the calculations or are people with a certain aptitude picked out in the beginning?

Thanks for all the answers btw!

No problem at all. Not often I get to hang around the military forum these days!! I am usually over in MMA, like you!!

Certain jobs and appointments require a soldier to be of a particular rank. There is no aptitude testing, as such, for specific roles but there are courses that must be completed in order to gain particular qualifications and these courses have tests that must be passed. A lot of the career paths have chained courses/qualifications in the Irish Defence Forces.

For instance a Gunner or Junior NCO that wants to be a Regimental Surveyor (one of the most technical roles) will first of all have to complete a Basic Gunnery course (12 weeks), then a year or two later he might take on a Battery Technical Assistants Course (8 weeks) and then finally, maybe another year or two later he will take on the Regimental Survery Course itself (10 weeks). All told he will have spent thirty weeks undergoing formal training and passing tests as well the practical ''real world'' experience he will gain with his unit in between the courses.

Officers cover most of the above mentioned courses in one continuous run as part of their Young Officers (YO's) Course.

There are a multitude of roles to be filled within an Artillery Regt. Some very technical, scientific and mentally challenging, some physical and labour intensive and some that are both. Guys tend to slot into a role that suits them and roles that they suit early enough in their careers.

discus

Basic Gunnery course (12 weeks)

:eek: My light gun course was 2 weeks. Irish Army seems quite good for courses. It was all pretty haphazard in the BA.

John_D80

discus wrote: »

:eek: My light gun course was 2 weeks. Irish Army seems quite good for courses. It was all pretty haphazard in the BA.

Now that I think about it, it might actually be only 8 weeks sorry. But the course covers, the L118, L119 and the RUAG 120mm mortar. There are absolutely no corners cut in fairness. All students get trained up to do all the jobs from No 2 to No 6 on all three weapons and they will get to fire all three weapons also.

They will also cover (and drill the **** out of) the more obscure things like quick actions and sniping/single gun actions also.

beauf

discus wrote: »

Correct. It's called "High Angle". When the 105mm is firing at a close target, it will elevate the barrel at a pretty steep (near vertical) angle. There are rules for firing on high angle, such as adding spoilers to the shells....

Whats a Spoiler on a shell?

discus

Imagine a small frisbee inserted onto the nose of a shell! Creates drag, with the intention of lowering the speed (and therefore range) of the projectile.

De Bhál

John_D80 wrote: »

Wow you must have fired at or close to max range at some stage!!

Very jealous!!

so I'm taking from this that in the Irish Army when been trained on this gun you never get to fire it to it's maximum range of 17.2km?

Not that that surprises me, as that's a long distance in a small country and you mightn't have the available free space. Just wondering is all.

Victor

Glen of Imaal is about 5 x 7km, so maximum range will be curtailed. That's not to say that people haven't fired elsewhere. http://www.openstreetmap.org/#map=13/52.9950/-6.5024

The Air Corp (Meath) and Naval Service (Cork x 2) have other ranges, but I doubt they are used by land-based artillery.

John_D80

De Bhál wrote: »

so I'm taking from this that in the Irish Army when been trained on this gun you never get to fire it to it's maximum range of 17.2km?

Not that that surprises me, as that's a long distance in a small country and you mightn't have the available free space. Just wondering is all.

That's correct. There is only one place in the country where we can fire Artillery weapons and that is The Military owned lands in The Glen of Imaal. The max range we would fire at would be about 5-6 kms`as far as I remember.

It would be nice to be able to test the weapons to their maximum but as we dont deploy field guns overseas, its not a priority for the Irish DF. I believe the Brits can fire up to around 13-14 km in Salisbury but I may be wrong here. Maybe discus can confirm this?

Edit: Also worth noting as well that max range is a misleading term actually. Usually the farthest range that would be fired at would be 85-90% of the actual max range. In the case of the 105 that would be about 15km. As you approach the actual max range accuracy is gretly affected.

gallag

Iv played enough angry birds to be considered a bit of an expert on targeting and angles etc, feel free to ask.

gallag

John_D80 wrote: »

That's correct. There is only one place in the country where we can fire Artillery weapons and that is The Military owned lands in The Glen of Imaal. The max range we would fire at would be about 5-6 kms`as far as I remember.

It would be nice to be able to test the weapons to their maximum but as we dont deploy field guns overseas, its not a priority for the Irish DF. I believe the Brits can fire up to around 13-14 km in Salisbury but I may be wrong here. Maybe discus can confirm this?

Edit: Also worth noting as well that max range is a misleading term actually. Usually the farthest range that would be fired at would be 85-90% of the actual max range. In the case of the 105 that would be about 15km. As you approach the actual max range accuracy is gretly affected.

Would the barrel have a short lifespan on max charge? Is that something that is counted or does it just get a visual/xray at service?

beauf

gallag wrote: »

Iv played enough angry birds to be considered a bit of an expert on targeting and angles etc, feel free to ask.

There was always this...

https://en.wikipedia.org/wiki/Gorillas_(video_game)

John_D80

gallag wrote: »

Would the barrel have a short lifespan on max charge? Is that something that is counted or does it just get a visual/xray at service?

Barrels do have lifespans yes. Cant rightly remembered exactly how it is measured but it is indeed all to do with the amount of rounds fired and especially the charges fired.

As Irish DF guns only ever fire at the lower charges (1, 2 and very very rarely charge 3) there has to date been minimal wear on the barrels and they have been in service since the late 80's.

The depth of the rifling in the bore is monitored by ordanance to keep track of wear.

What happens when that depth is deemed to be too shallow? I actually dont know. But I would have to assume there could be a certain amount of re-rifling before a barrell is disposed of.

discus

Barrel diameter increases as more rounds are put through them. This barrel diamter is measured periodically and that info is given to the command post. Naturally, a barrel that isnt as snug for a shell will unfortunately lets the pressurised gases escape during firing, and so the shell wont fire as far as it should... The CP use this info. Not sure about max firing distances on current ranges. Had a blast in america though, you can do anything on their ranges...

Stovepipe

Firing at max charge also has a higher wear effect on the recoil equipment and the gun frame. It's why it's not routinely fired in peacetime, because the gun would need a depot level overhaul after a sustained period of charge five. Barrels are lifed for firing wear but can also be rejected for cracks or corrosion (one reason why guns and mortars are washed out after firing. The products of combustion can be corrosive so the barrels have to be cleaned......I once took part in an examination of Army 81mm mortar barrels. We found lots of cracks, in two sample tubes so they were all withdrawn in short order........my late grandfather took part in firing the 6 and 9.2 inch guns at Fort Davis in Cork, decades ago. They used to fire out to a designated maritime range area, which no longer exists. There was a range board there, in the 80s, which listed all of the towns,villages and important points around Cork Harbour that they knew they could hit. Few people realised that a lot of the guns could face inland and were quite surprised how far they could reach. This, with WW1 era guns.....if our Army wanted to do a long range shoot, there is nothing preventing them from firing out to sea. The NS still uses a maritime range area, that a 105 could probably reach.

tac foley

The covered items on either side of the barrel at the breech end are balancing springs. They are not part of the recoil system. They enable the gun to be elevated or depressed easily and under control - crank the elevating wheel and see what I mean. Try cranking the elevating wheel without them and see what I mean.

By the way, the British Army does not fire its artillery in Salisbury - the citizens of that fine old city and its beautiful cathedral would be really. p****d off if you did that.

Instead, the gunners use the facilities of The RA Centre at RSA Larkhill, and the adjacent Salisbury Plain TA.

tac

tac foley

In the British Army, gun barrels are not re-rifled. They ARE cast, a term used to indicate scrapping. Needless to say, the barrels ARE returned to the makers for melting down and recovery into new barrels.

tac

tac foley

I'm surprised that nobody has so far mentioned 'yaw'.

Great fun can be had discussing that....

tac

John_D80

tac foley wrote: »

I'm surprised that nobody has so far mentioned 'yaw'.

Great fun can be had discussing that....

tac

Years since Ive even heard that term. Something to do with the projectile drifting offline because of the spinning motion I think.

Gold star for me sir?

tac foley

Aluminum.

Almost correct. It is the tendency of the base of the projectile to try and overtake the front at extended ranges - sort of skidding, if you will.

And coupled with the rotating earth problem. It is rotating at 1000 mph, after all, and must be taken into consideration.

Basically, if you have a gun sited on the equator, and you shoot directly east, the proj will fall short, as the earth moves away from the projectile from the split second of shot ejection. Your shot will land short. The opposite is true if shooting directly west.

Shooting north and south to any degree compounds the problem, as does the position of the gun and its relative angle to the equator at any point on the geoid.

Obviously, the further that you are shooting, the greater the effect.

Basically, gunners 'assume' that the earth is actually a perfect sphere, instead of an oblate spheroid, totally ball-like and devoid of extraneous features like hills, valleys, mountains and so on. The gunner simply fires a projectile at an imaginary point on the geoid, hoping that the path of the projectile will intersect the surface at the imaginary point on the geoid that is contiguous with an an actual target by the time that the proj actually gets there. We are looking, therefore, at a whole bunch of happy/unhappy [depending which end of the event you are] coincidences - all taking place simultaneously.

Succeeding in this endeavour is called 'a hit'. Failing to do so is called 'a miss'.

The first is good.

The second is not.

These days the little box you see the FCO holding does it all for you, but there are still places where 'steam artillery' is taught, just in case that handy little gizmo goes futz.

The Royal School of Artillery at Larkhill introduces you to the Art AND Science of gunnery by figuratively removing the batteries from the gizmo.

The shot plotting board, a piece of string and a double-ended grease pencil will be your friends.

Oh, and a compass.

tac

De Bhál

tac foley wrote: »

Basically, if you have a gun sited on the equator, and you shoot directly east, the proj will fall short, as the earth moves away from the projectile from the split second of shot ejection. Your shot will land short. The opposite is true if shooting directly west.

That's very interesting.

Stovepipe

it's why airliners fly great circle routes over the globe. If you flew in a dead straight line, your destination would have moved and would not be there when you got there...

tac foley

TBH, it's nothing less than magic that anybody manages to hit anything at all. When I used to take my students to Larkhill, it was in the hope that a FCO/FOO course was on at the same time. It was great craic to actually fire the AS90 [155mm SPG] from a remote point standing about fifteen metres behind the gun and using the remote control, just like a giant toy, and watch the 95 pound 'bullet' exiting the barrel and disappearing into the sky, to land, hopefully, within the boundaries of the Larkhill/SPTA.

As some of you know, I shoot big old rifles for fun, but nothing compares with shooting a £1200 'bullet' or three.

tac

discus

HE shells cost a lot more these days Tac!

The shot plotting board, a piece of string and a double-ended grease pencil will be your friends.

Oh, and a compass.

It's actually quite easy! I preferred it tbh. Putting a target grid reference, a weapon and a dispersal into a Fire Control Computer gets boring. You are constantly working when you have reverted to manual computation. Not that I got to do it all that much - Too busy being recce driver, signaller, safety assistant and chief Wets and Bacon Butty man.

De Bhál

OK another basic one...say there's a scenario where you're missing your target but finding the range so you're landing right or left of the target; does the gun rotate kind've like how a tank gun rotates to aim better or do you have to pick up the whole gun and roll it around until you're in line with the target?

discus

The barrel can be rotated (aka traversed) left and right a certain number of degrees using the traversing wheel, but if it gets too far, the gun is centred, and re-aligned to the target by lifting and shifting. So in short, it uses both.

tac foley

discus wrote: »

HE shells cost a lot more these days Tac!

Well,

a. this was while back, and

b. they were out-of-date/PSBD shells of an old design found in a storage bunker they had forgotten about. The find included 15,000+ 5.5" as well, so they resurrected a bunch of gate-guardians and museum exhibits to give the troop the experience of shooting a REAL steam-era and LARGE field gun. No mechanical help whatsoever with that lovely old piece. Only mandraulic.

tac

gallag

When you think how difficult it is to land artillery on target from land I wonder how much harder it is from a ship? Surley a rocking ship makes things harder? Auto hydraulic levelers?

tac foley

Gyroscopic stabilisers, as seen on modern main battle tanks.

tac