Artillery: News & Discussion

ramana · Post by **ramana** » 28 Jun 2017 21:54

Agreed for each type of shell.
The shells from different mfg and production lots are accepted based on Lot Acceptance Tests.

So one set of firing tables for each of the shells.
That is what being developed now.

Katare · Post by **Katare** » 29 Jun 2017 01:00

I just looked up the science for simplistic understanding of drag's impact. This is extremely simplified example with a lot of assumption, focus is to see the effect of altitude/density change and assume rest are constant at both location.

The equation is D= Cd X A X r X V^2 X 0.5

Fire two bullets from the same gun at different elevations, one at sea level and the other at some higher altitude where air density is 20% lower.

Since it's the same type of bullet fired at sea level and at higher altitude we can leave out Cd (depends on aerodynamics of the bullet shape) and A (roughly surface area of the front of the bullet).

So what's left is D= r X V^2 X 0.5

r is density of air and V is the velocity of the bullet. So 20% reduction in r should reduce the drag by 20% but now the bullet would maintain a higher average velocity because it's dealing with a smaller drag force. Since the drag increases as square of velocity the average drag over the entire length of bullet would increase substantially to reduce the gain achieved by low density air.

These two factors work against each other and must intersect at some point on range scale so far 20% reduction in r (air density) we would have range increase of less than 20% but it should be more than what it would be at the sea level ( all other points ignored/constant). Since the actual range is dependent on the bullet shape, gun wear, local temp, humidity, wind and density of air, the only good way might be to make charts and tables at key reference locations and that is why they are doing it.

Example -

Sea level
- Air density 1 (assumption)
- Average bullet velocity 3 Km/second

High altitude
- Air density 0.8 (20% lower)
Average velocity - 3.6 km/second ( assuming 20% higher)

Sea level Drag = 1*3*3/0.5 = 18 drag units
Altitude Drag (20% higher average velocity) = 0.8*3.6*3.6/0.5 = 20 drag units (this can't be true, the number should be lower than 18)
Altitude Drag (10% higher average velocity) = 0.8*3.3*3.3/0.5 = 17.424 drag units (if this is correct assumption the increase in range would be proportional to the difference between 18 and 17.424

So in a nut shell lower drag, at high altitude, would increase average velocity (the bullet would loose speed slowly)
This increased average velocity would increase the drag as a square of change in velocity
Since these forces would work against each other the net gain in range should be small/marginal, if my math is right. Since the bullet at different air density would have different speed profile and hence drag profile, the results would need to be charted on a graph and than converted into usable numbers by some algorithm.

ramana · Post by **ramana** » 29 Jun 2017 04:38

Supersonic drag and lift are different. Function of mach number and length of the shell. I will find the formulae latter but generally, shells experience more lift at altitude leading to overshoot. Hence need to have firing tables for mountains.

Bishwa · Post by **Bishwa** » 29 Jun 2017 07:27

Artillery guns do exhibit longer range at high altitude.

As per Major Praveen Shawneys "Himalayan Conflict Forges Artillery Doctrine"

"Once stabilized (in siachen base camp), the FH-77B has shown itself to be both accurate and consistent, achieving a range of 42km from altitudes of 12,000ft using High Explosive Extended Range (HEER) base bleed ammunition."

In the plains the figures for the FH-77B is much lower even with HEER

Katare · Post by **Katare** » 29 Jun 2017 08:12

I only considered drag forces and used simple formula given at the NASA website. I am not sure what else would change, if both gun and target are at the same altitude? You can get much longer ranges if you shoot from mountain top at targets located at bottom of the mountain. At siachen indian positions are located at much higher altitude than Pakistani positions so our guns would shoot much longer but that is a result of geometry not altitude.

I'll be interestd in learning how/why lower density of air would increase/create lift in a symmetrical shape bullet? To generate lift forces you need asymmetrical structures like wings of an aircraft to get the different air velocity at its surface. How would one generate lift in a rotating symetrical wing less bullet? Can one generate lift on a fast moving sphere?

Bishwa · Post by **Bishwa** » 29 Jun 2017 08:21

This is another data point on the impact of high altitude on a bullet

"The increase in efficiency causes bullets to strike higher on the target
at high altitude than at sea level. At an elevation of 10,000 feet (3,050 m), a round fired
at a target at a distance of 1,000 meters will impact almost 70 inches higher than at sea
level."

Source : High altitude warfare: the Kargil Conflict and the future, Acosta, Marcus P.
Monterey, California. Naval Postgraduate School

Katare · Post by **Katare** » 29 Jun 2017 08:42

That makes sense, because higher average velocity at higher altitude would give gravity lesser time to pull it down so it will hit higher at target.

Singha · Post by **Singha** » 29 Jun 2017 09:01

70 inches over 1km is HUGE offset. some serious recalibrating of gunsights will be needed even at typical 200-300m rifle ranges

tsarkar · Post by **tsarkar** » 29 Jun 2017 18:38

shiv wrote:
tsarkar wrote:Field Trails is an all encompassing term, but in context of M777, it's preparation of ballistic tables and Standard Operating Precedures for regular units. The same is being done for Dhanush too.
Thank you. So it is not about importing first and then finding out if it works.

http://indiatoday.intoday.in/story/m777 ... 84904.html

To witness the field testing of newly acquired Howitzer, a US made gun, an India Today team traveled for more than 600 km from Jaipur to Jaisalmer.

At the location, the India Today team witnessed the formation of firing table. A firing table is formed to collect and collate data which can be used later during field firing. Every shot fired from the Howitzer gun was recorded. The trajectory, its speed, frequency, range, etc, was being monitored and the data recorded.

As per the contract agreement, firing tables are being prepared by the contracted agency - US Government and BAE GCS Ltd with support of Indian Army.

Researchers and personnel from US, Switzerland, and BAE systems were present at the location to assist the Indian Army in collecting the data. This data is considered significant for accurate firing during actual usage.

It can use all types of 155 mm ammunition. However, currently, its being tested on four types of 155 mm ammunition, including the HE, the smoke, the illumination and the fire bust.

http://www.financialexpress.com/india-n ... ow/674221/

According to IE, the M777 guns have been designed to fire Indian ammunition in Indian conditions.

http://www.thehindu.com/news/national/t ... 490830.ece

“Two M777 A-2 (Indian) ULHs arrived today for preparation of firing tables. During this event, the guns will fire 155-mm indigenous ammunition. As per the contract agreement, firing tables are being prepared by the contracted agency — U.S. government and BAE Systems with support of the Army,” the Army said in a statement.

The Indian suffix connotes India specific customizations. Every customer has specific requirements, so equipment have designations like Mirage 2000H (Hindustan) Mirage IIIEP (Pakistan), Su-30MKI, MKM (Malaysia) MKA (Algeria).

After firing tables are ready, three more guns will be received in in September for training purpose, the statement said.

Another officer explained that range tables are required when integrating local ammunition with the gun and calibrating it against variables such as weather and temperature.

Dhanush, an upgraded and indigenous version of the Bofors gun, is in the final stage of trials and induction is slated to begin soon.

So there is no conspiracy against Dhanush, and its field trials are firing tables being prepared and its users trained. It is actually ahead of the curve of M777 for induction.

Lastly folks, please appreciate the systematic approach of preparing firing tables and training users as a precursor to induction.

If such detailed reporting was not present, members would've gone bonkers with superstitious conspiracy theories of "field trials after induction."

tsarkar · Post by **tsarkar** » 29 Jun 2017 18:43

The IFG/LFG is a great gun but its time to move on with Dhanush & ATAGS.

rohitvats · Post by **rohitvats** » 30 Jun 2017 00:11

I've often repeated this on BRF - there was a time when divisional artillery brigade had 3 x Field Regiments and 1 x Medium Regiment. Medium was M-46 or Bofors. Field was IFG. But during 90s, most of these field Regiments we're converted to medium role. Break-up of USSR made 100s of M-46 available on cheap. IFG/LFG are used as required - mountain division still has more 105mm caliber than medium guns. M-777 is NOT a replacement for IFG/LFG - it adds medium category firepower for which M-46 was being earlier used. A role it is not suited for given gun angle issues. M-46 is field artillery for plains. We will definitely see some new 105mm avatar in IA service.

Singha · Post by **Singha** » 04 Jul 2017 21:40

https://www.liveleak.com/view?i=170_1498999087

brar_w · Post by **brar_w** » 04 Jul 2017 21:45

Here's the same DV release on YT -

Singha · Post by **Singha** » 04 Jul 2017 21:53

takes 10 men per gun

brar_w · Post by **brar_w** » 04 Jul 2017 22:06

Yup and the Marines had to have it this way because they put a 4500 kg not to exceed weight limit (compared to 7300 kg for the howitzer it replaced) on the weapon which dictated the configuration and how much advanced technology they could roll in both due to the weight itself, but also due to the fact that a lot of its cost was driven by the increased use of Titanium.

Prasad · Post by **Prasad** » 04 Jul 2017 22:44

What is that mounted at the end of the gun like a bayonet?

negi · Post by **negi** » 04 Jul 2017 22:51

^ That's a projection with a hole for towing.

brar_w · Post by **brar_w** » 04 Jul 2017 22:52

Yes, a tow catch -

Khalsa · Post by **Khalsa** » 05 Jul 2017 03:22

Woah

Gun being towed with barrel towards the direction its travelling in
Cool, haven't seen that before.

Is it a better handling for hairpin bends in J&K especially Ladakh area

brar_w · Post by **brar_w** » 05 Jul 2017 03:30

Rakesh · Post by **Rakesh** » 16 Jul 2017 07:41

M-777 Ultra Light Howitzer
http://tejasmrca.weebly.com/land-system ... t-howitzer

ArjunPandit · Post by **ArjunPandit** » 16 Jul 2017 08:02

Rakesh wrote:M-777 Ultra Light Howitzer
http://tejasmrca.weebly.com/land-system ... t-howitzer

rakesh saar the page is getting blocked due to some proxy issues or appropriate site warning from company laptop

Rakesh · Post by **Rakesh** » 16 Jul 2017 08:21

Arjun Saar, I just checked the link. I am not facing the issue. Can you and others please try again from your home computers? Your company probably does not allow access to sites like this.

jamwal · Post by **jamwal** » 16 Jul 2017 12:09

Weebly is ablog hosting service somewhat like Wordpress, blogspot and banned in some networks.

Singha · Post by **Singha** » 16 Jul 2017 20:11

Why dont they develop a moto mod type crane module which can be transported in another sling or trailer and ease the burden

jamwal · Post by **jamwal** » 16 Jul 2017 20:43

Wouldn't pulling the gun by barrel damage it ?

Rakesh · Post by **Rakesh** » 16 Jul 2017 21:04

Ultra-light howitzers: Exhaustive field trials on in Pokhran
‪https://www.google.ca/amp/m.economictim ... 617323.cms

brar_w · Post by **brar_w** » 16 Jul 2017 21:44

jamwal wrote:Wouldn't pulling the gun by barrel damage it ?

Not unless it has been designed to be done that way.

Pratyush · Post by **Pratyush** » 16 Jul 2017 22:37

jamwal wrote:Wouldn't pulling the gun by barrel damage it ?

The d 30 and the massive russian 240 mm mortars have the tow hook in the same position. As does the ST pegasas so it is an accepted solution for towing the gun.

JayS · Post by **JayS** » 16 Jul 2017 22:48

DDR of Sjha tweets that there has been a burst of muzzle of the barrel happened for Dhanush during trials. Majaor incidence was avoided. No more info than this.

darshan · Post by **darshan** » 17 Jul 2017 03:36

how much worse will the Pokhran test range would be compared to many test ranges like Yuma or ones in Africa?

Khalsa · Post by **Khalsa** » 17 Jul 2017 10:18

darshan wrote:how much worse will the Pokhran test range would be compared to many test ranges like Yuma or ones in Africa?

huh ?
what

shiv · Post by **shiv** » 17 Jul 2017 10:28

darshan wrote:how much worse will the Pokhran test range would be compared to many test ranges like Yuma or ones in Africa?

What makes you think it is worse? Too many shivering doubts

Pratyush · Post by **Pratyush** » 17 Jul 2017 12:52

shiv wrote:
darshan wrote:how much worse will the Pokhran test range would be compared to many test ranges like Yuma or ones in Africa?
What makes you think it is worse? Too many shivering doubts

Well if pokhran is worst compared to other test sites. Then in a perverse way it is a badge of TFTAness.

No.

JayS · Post by **JayS** » 17 Jul 2017 14:36

JayS wrote:DDR of Sjha tweets that there has been a burst of muzzle of the barrel happened for Dhanush during trials. Majaor incidence was avoided. No more info than this.

I wonder if this was same as TOIlet paper below reported on May 27, 2017.

Indian Bofors misfires during trials

http://timesofindia.indiatimes.com/city ... 864288.cms

In the second such incident, one of the Indian guns was damaged due to an accident during test fires. Nearly a fortnight ago, as battery trials of Dhanush — the Indian gun were under way at Pokhran — the shell burst soon after ejection from the barrel, said sources.

They say this has damaged the muzzle brake, the part at the front of the barrel. Its function is to absorb recoil created during firing of shells. The howitzers are being made at the Gun Carriage Factory (GCF), Jabalpur. Around 12 pieces have already been made.

This incident has pushed the process back by a month. It happens when the GCF was in the last stage of trials. The firing was part of user exploitation, which was conducted for the first time for any weapon system.

Usually, once a system is cleared through user-trials, it is inducted. "For Dhanush, user exploitation was included after user trials were over," said the sources. This means the army wanted to further use guns to get accustomed to it. Any changes required were also supposed to be suggested.

Was this posted here previously..? If, yes I missed it completely.

PS: India Today also tweeted this yesterday. Not sure if they all are referring to same incidence or there were two similar incidences in which muzzle was damaged. I think its the same incidence.

https://twitter.com/IndiaTodayFLASH/sta ... 2571970560

But I can't find the tweet by DDR. May be its deleted..? Can't find it or see it on their TL. Wonder why. I do have its screenshot on cell phone though.

putnanja · Post by **putnanja** » 17 Jul 2017 15:19

Wasn't the earlier incident due to an issue with the shell and not the gun per se?

Marten · Post by **Marten** » 17 Jul 2017 15:22

putnanja wrote:Wasn't the earlier incident due to an issue with the shell and not the gun per se?

Nothing to suggest that it was not the shell again. "Burst just outside the barrel" or "soon after ejection" would indicate shell quality is suspect; nothing to do with Dhanush itself.

JayS · Post by **JayS** » 17 Jul 2017 15:35

Marten wrote:
putnanja wrote:Wasn't the earlier incident due to an issue with the shell and not the gun per se?
Nothing to suggest that it was not the shell again. "Burst just outside the barrel" or "soon after ejection" would indicate shell quality is suspect; nothing to do with Dhanush itself.

The 2013 (IIRC) incidence was due to faulty ammunition. This one might as well be due to faulty ammunition. At least seems so from the reading. The damage seems less this time.

JayS · Post by **JayS** » 17 Jul 2017 15:42

Interestingly the article posted above says:

Usually, once a system is cleared through user-trials, it is inducted. "For Dhanush, user exploitation was included after user trials were over," said the sources. This means the army wanted to further use guns to get accustomed to it. Any changes required were also supposed to be suggested

I have been wondering the extended time for "proof" trials for production version artillery pieces (posted my doubt here once). May be the stretched testing is because of this "User exploitation" tests which are over and above the usual set of tests for merely proving the production version. Its good that time is taken and the changes are being suggested upfront. But I hope the changes are limited in scope only to avoid project creep.

srai · Post by **srai** » 17 Jul 2017 16:54