Vertical range for machine guns

[centurion]

What was the vertical range for the Maxim Mg08, The Vickers Mg and the Hotchkiss? ie when used in the AA role what was the ceiling above which an aircraft would be relatively safe from them? Obviously this would be less than their range when used against ground targets and presumably there would be a difference between forming a protective curtain of fire and aiming specifically at a target. I do have one source that gives a figure but without any further reference as to where it comes from (in any case I am becoming wary of using single sources and would like to get a cross bearing so to speak). Has anyone come across any official range tables or the like?

[TonyE]

A number of experiments have been carried out on the maximum vertical range of various calibres of ammunition, notably by Maj. Gen. Julian Hatcher in the early 1920s. (see "Hatchers Notebook", pp.510-518. Others are J.W.Hicks in 1919 and R.L.Tippins in 1910.

The British military concluded that the Mark VII bullet when fired vertically rises to 9,000 feet, taking 19 seconds to ascend and 36 to descend giving a time of flight of 55 seconds. These figures were also agreed by Tippin and Hicks.

Hatcher claims the Germans give similar figures for the 7.92mm, claiming a rise to 9,000 feet, taking 19 seconds to ascend and 38 to descend, total 57 seconds. I suspect there is a slight error in the height given the higher muzzle velocity of the 7.92mm and the longer descent time, but it broadly confirms the figures.

Experiments showed that if fired vertically the bullets returned to earth base first, but there was a crtical angle of elevation below which the bullets followed a normal trajectory and landed nose first.

I don't have any data on the practical maximum vertical height for anti-aircraft fire. I am sure there is a Vickers manual that gives such elevation data though.

Regards

TonyE

[centurion]

Thanks for this. The P,P2 and M Caquot observation balloons with a 2 man crew had a practical maximum ceiling of 5,000 ft or thereabouts this being effectively limited by the weight of a steel mooring cable sufficiently long. The R could get slightly higher but not in the 3 man crew configuration. An article published by Stanford University based upon the papers of a former Stanford man who served as an observer in an American balloon unit states that at 5,000 feet the balloon was above the effective ceiling of the defending machine guns (the Americans appear to have primarily depended upon dedicated machine gun crews for their balloon defence). 5,000 feet didn't seem much to me. Given the above figures of 9,000 feet maximum possible 'range' (and I am assuming that the Hotchkiss was not dissimilar) I wonder what the limiting factor was. I assume that whatever it was it would also apply to German, British and French balloon defences.

[TonyE]

Having delved a bit deeper into "Textbook of Small Arms 1929" (the British military ballistics "bible") I found the following amongst various range tables.

Based on a bullet with a sectional density of 0.284 and a muzzle velocity of 2,600 fps (.303 Mark VII bullet is 0.26 and 2,450 fps) and fired at an elevation of 40 degrees the vertex height is 4,962.2 feet with a time to vertex of 13.74 seconds and a residual velocity of 300 fps.

Beyond that elevation range decreases but maximum height of vertex increases to 9389 feet after time of flight of 19 seconds.

A flight time of 19 seconds and a residual velocity of almost zero is not conducive to good AA gunnery.

I would suggest a fighter attacking a balloon moored at 5,000 feet from a height of 6,000 feet would be pretty safe from MG fire.

Regards

TonyE

[centurion]

Makes sense especially as the preferred tactic was to attack from above in a near vertical dive so that the balloon itself shielded the attacker from any guns too close in to the balloon

[Stoppage Drill]

Small arms ground fire has never been a particularly effective form of antiaircraft defence, pace Popkin, but it is frightening. Even today it can be quite amusing to watch AFV commanders trying to whack a radio controlled model aircraft with cupola mounted machine guns. Fear factorwise, the more tracer, the better.

Vertical range is not a practical consideration - a machine gunner will only engage a low flying target, will probably not have a mount which allows vertical fire, and will be shooting at little more than 45 degrees usually.

[Chris Henschke]

From a doctrinal point of view, it seems that 3,000 feet was the maximum range for effective fire.

These are some quotes from Instructions for the use of the Forward Area Anti-Aircraft Sight for Lewis, Vickers and Hotchkiss Guns, released as SS 142 in June 1918. (This sight replaced the Hill Jackson Sight.)

"The Inner Ring gives the necessary “aiming off” for firing at aeroplanes flying at an altitude of 200 feet (the normal low-flying machine gun aeroplane).

The Outer Ring gives the necessary “aiming off” for firing at aeroplanes flying at an altitude of 1,000 feet (the normal contact aeroplane).

The Outer Ring should be used for firing at all aeroplanes at an altitude of from 500 feet to 3,000 feet; the inner ring for all aeroplanes at altitudes less than 500 feet."

It later states in Section 5;

"Control of fire.—Do not waste ammunition on aeroplanes which are out of range. By day a machine is only in range as long as the struts or Iron Crosses are visible to the naked eye.

At 3,000 feet the side view of the struts and Iron Cross are visible to the naked eye."

[dman]

Rule of thumb for estimating the EFFECTIVE RANGE (range at which have reasonable chance of hitting target and inflicting damage) for an AA

weapon is: 1 meter per mm of weapon cailber

Small arms 8 mm cailber = effective range of 800 meters

During Falkland Island War (1982) many Briitsh ships used hastily mounted 7.62 machine guns (including some upgraded WW II Brens!) to fire

on attacking Argentine jet aircraft (A4 Skyhawks, Mairage 3/5, Daggers )

Were able to hit and damage many of the aircraft - shooting down several .

Problem (found out during WW II ) was that small arms dont have range and "hitting power" to stop an attacking aircraft - may inflict damge, even

lethal damage to aircraft, but still will be able to bomb/strafe target

Kamikaze attacks showed that 20mm were ineffective at stopping such attacks

One can point out that WW I aircraft were much slower making them easier target to hit and the construcion - wood/fabric with unprotected fuel tanks

and no armour for pilot/vital systems made them more vulnerable to ground fire.

[TonyE]

Small arms ground fire has never been a particularly effective form of antiaircraft defence, pace Popkin, but it is frightening. Even today it can be quite amusing to watch AFV commanders trying to whack a radio controlled model aircraft with cupola mounted machine guns. Fear factorwise, the more tracer, the better.

Vertical range is not a practical consideration - a machine gunner will only engage a low flying target, will probably not have a mount which allows vertical fire, and will be shooting at little more than 45 degrees usually.

I too have played the silly game of trying to shoot down model aircraft with an MG, but that is in a modern context. In WWI aircraft were lower, slower and more vulnerable to ground fire.

Also. contrary to your comment, there were plenty of mounts suitable for anti-aircraft fire. As well as the Lewis mount shown above, the Royal Navy developed a number of AA mounts.The pictures are taken from the Admiralty Technical Index and History of Gunnery published in May 1920. A considerable section is devoted to AA gunnery including mounts, special AA sights and how to use them. The mounts are for both Lewis and Maxim (The RN never used the Vickers in WWI despite the picture).

I apologise that the pictures are so dark, but my copy of the history is an old photocopy.

Regards

TonyE

..

[Steven Broomfield]

This may sound a silly question, but is firing vertically a Good Idea?

[Neil Mackenzie]

Steven. I was just thinking the same thing. On the basis of what goes up must come down!!

[TonyE]

True, but given the effect of wind the bullet will land some way away. Also tests carried out in the 1920's showed the bullet landed at low velocity and was unlikely to cause serious injury.

Regards

TonyE

[MikB]

True, but given the effect of wind the bullet will land some way away. Also tests carried out in the 1920's showed the bullet landed at low velocity and was unlikely to cause serious injury.

Regards

TonyE

Something I read years ago in New Scientist gave the velocity of a returning 7,62 as just over 100 m/s on reaching the surface in still air. That runs out about 35-odd foot-pounds kinetic in Imperial, and is quite enough to cause serious or fatal injury to an unprotected human head. WW1 calibres can be expected to behave roughly similarly.

I also heard (with less certainty of source) that when the PLO left Beirut in the 1980s with much firing of Kalashnikovs into the air, quite a number of people were killed by falling bullets over the period, mostly kids out looking for water.

Falling bullets fired in volume need to be taken seriously when there are people out in the open.

Regards,

MikB

[centurion]

I too have played the silly game of trying to shoot down model aircraft with an MG, but that is in a modern context. In WWI aircraft were lower, slower and more vulnerable to ground fire.

Also. contrary to your comment, there were plenty of mounts suitable for anti-aircraft fire. As well as the Lewis mount shown above, the Royal Navy developed a number of AA mounts.The pictures are taken from the Admiralty Technical Index and History of Gunnery published in May 1920. A considerable section is devoted to AA gunnery including mounts, special AA sights and how to use them. The mounts are for both Lewis and Maxim (The RN never used the Vickers in WWI despite the picture).

I apologise that the pictures are so dark, but my copy of the history is an old photocopy.

Regards

TonyE

..

The German produced some mounts in which the gunner lay on his back in a revolving cradle and reached up to the gun

[centurion]

Something I read years ago in New Scientist gave the velocity of a returning 7,62 as just over 100 m/s on reaching the surface in still air. That runs out about 35-odd foot-pounds kinetic in Imperial, and is quite enough to cause serious or fatal injury to an unprotected human head. WW1 calibres can be expected to behave roughly similarly.

I also heard (with less certainty of source) that when the PLO left Beirut in the 1980s with much firing of Kalashnikovs into the air, quite a number of people were killed by falling bullets over the period, mostly kids out looking for water.

Falling bullets fired in volume need to be taken seriously when there are people out in the open.

Regards,

MikB

The greatest number of civilian deaths in Baghdad in one night as a result of the Iran/Iraq war was not because of any Iranian air raid but from the feu de joie on the night the cease fire was announced and lots of people went out in the streets and just blazed away into the sky with rifles. It was a hot night and many families were sleeping on the flat roof tops.

Given that observation balloons were located 3 - 5 miles behind the front line and the Americans at least used lots of machine guns to provide AA protection during an attack there must have been a lot of bullets falling on friendly territory. Being in the vicinity of a balloon may not have been healthy.

[TonyE]

Something I read years ago in New Scientist gave the velocity of a returning 7,62 as just over 100 m/s on reaching the surface in still air. That runs out about 35-odd foot-pounds kinetic in Imperial, and is quite enough to cause serious or fatal injury to an unprotected human head. WW1 calibres can be expected to behave roughly similarly......

Regards,

MikB

That correlates very well with the results Hatcher obtained in the 1920s when he found returning .30 calibre bullets had a velocity of about 300 fps. Those were flat based bullets so I would expect a boat tailed 7.62mm L2A2 bullet to have a slightly better ballistic coefficient when reversed and so return with a slightly higher velocity.

I was perhaps being a little loose with my terminology when I said returning bullets were unlikely to cause serious injury. I should have said lethal injury.

Hatcher did his firing from a raft in the middle of a lake, and some rounds hit it on their return. He states that one hit the edge of the wooden raft and bounced into the water, leaving a mark about 1/16 inch deep in the soft pine board. Two others hit a bucket of water and left a "barely perceptable dent in the bottom".

My comments were based on Hatchers statement "It was concluded from these tests that the return velocity was about 300 feet per second. With the 150 grain bullet, this corresponds to an energy of 30 foot pounds. Previously the Army had decided that on the average, an energy of 60 foot pounds is required to produce a disabling wound. Thus service bullets returning from extreme heights cannot be considered lethal by this standard."

That also matches with today's thinking. 30 ft/lbs is 40 joules which is half the standard 80 joules considered necessary for disablement.

regards

TonyE

[centurion]

I've a feeling that "Previously the Army had decided that on the average, an energy of 60 foot pounds is required to produce a disabling wound" had referred to the results of evaluations on the Brodie - in other words it would take 60 foot pounds to kill or disable (knock out) you if protected by one.

[Rockdoc]

In a document dated 17th January, 1917, that covers the AA defence of Salonika, the AA MG Sections are cautioned thus:-

General Rules

The AA MG Sections cannot and should not fire against aircraft except when flying at low altitude; in particular against Squadrons of aeroplanes profiting by favourable nights or by the first minutes of daylight. MG fire, when used, should be directed with the maximum rapidity.

Conditions for Opening Fire

Fire ought not to be opened unless the following conditions are fulfilled:-

1. Certainty that the objective is an enemy one
   
2. The diameter of the aeroplanes should appear greater than or equal to 8 mm (equals the distance of 1000 metres or under)
   
3. A dirigible should appear very close at hand
   

Zones of Fire

Falling bullets should be prevented from reaching those targets which it is desired to protect; but MG fire above these targets is not forbidden.

Later in the same section, it suggests that a strip of cloth be set up between two posts to indicate the unsafe angles of fire for the MG gunners to avoid. Somewhat pedantically, IMO, it uses as examples of areas where bullets should not fall hospitals and ammo dumps!

Keith.

[TonyE]

I've a feeling that "Previously the Army had decided that on the average, an energy of 60 foot pounds is required to produce a disabling wound" had referred to the results of evaluations on the Brodie - in other words it would take 60 foot pounds to kill or disable (knock out) you if protected by one.

You may be right, but 60 foot pounds is about 81 joules and 80 joules id the recognised energy level that needs to be delivered to incapacitate.

Regards

TonyE

[bill24chev]

So a "fig Roll" with an energy value of about 300j is a lethal weapon

[MikB]

You may be right, but 60 foot pounds is about 81 joules and 80 joules id the recognised energy level that needs to be delivered to incapacitate.

Regards

TonyE

Those folk in Beirut, Baghdad, and other places rained on by falling bullets are nevertheless dead, and the returning Kalashnikov bullet almost certainly has less of everything than Hatcher's 30 cal example. By the way, it's entirely possible that the New Scientist article I recalled was quoting Hatcher's findings - the article was prompted by by reader enquiries about risks from joy-shots - but there was additional material about the nature and severity of the injuries which I don't now remember.

Regards,

MikB

[Radlad]

Those folk in Beirut, Baghdad, and other places rained on by falling bullets are nevertheless dead, and the returning Kalashnikov bullet almost certainly has less of everything than Hatcher's 30 cal example.

Regards,

MikB

But you are assuming that all the 'celebration' Rounds are fired vertically and that is certainly not the case. A round fired at 45 degrees elevation will be much more deadly . The victims of many of these rounds will have been effectively in a beaten zone or will connect directly with careless bulllets fired from the street if they are observing from rooftops. Bad example Mik?

[MikB]

But you are assuming that all the 'celebration' Rounds are fired vertically and that is certainly not the case. A round fired at 45 degrees elevation will be much more deadly . The victims of many of these rounds will have been effectively in a beaten zone or will connect directly with careless bulllets fired from the street if they are observing from rooftops. Bad example Mik?

Well, I don't know that any round fired at or above 45 degrees would be more dangerous. They would still be more or less spent for horizontal velocity, and dropping at a steep angle from a lower height, so might even be less energetic except maybe for having reached terminal velocity for an object of that size, mass and form falling under 1g through atmosphere.

Such ballistics would be pretty difficult to verify either way without a substantial experiment. Mythbuster tried something similar a couple of years back and got rather uncertain results.

The point I'm trying to make is that it's unsafe to ignore the risk if there are friendly personnel about in the landing area.

Regards,

MikB

[centurion]

You may be right, but 60 foot pounds is about 81 joules and 80 joules id the recognised energy level that needs to be delivered to incapacitate.

Regards

TonyE

According to research trials carried out at Cranfield Department of Engineering Systems and Management (tor the Defence and Security Sectors) in 2009 by Steve Champion and others this 80 joules figure to incapacitate is "too simplistic and that the ability of a projectile to incapacitate is dependant upon where it impacts the body and how much energy is absorbed during the impact " A relatively hard object hitting the head needs less velocity than a softer one (say an old fashioned musket ball) hitting a fleshy part of the body. Thus the figure varies some way either side of 80 depending on circumstance and it's probably not a good idea to get hit on the head by a falling round.

[TonyE]

I have not seen the paper by Steve Champion, (but I will look it up next time I am the Defence Academy library) but it seems a sensible conclusion. I have always understood that the 80 joule figure for incapacitation was the absorbed energy figure anyway.

A bullet striking with an energy of say 120 joules yet exiting with a remaining energy of 80 joules has only delivered 40 joules, half the incapacitating level. Also, a bullet delivering 80 joules to a limb will certainly be incapacitating but likely to be less lethal than the same energy or less delivered to an unprotected head.

With regard to firing less than vertically, Radlad makes a good point. A stable bullet fired truly vertically will still be spinning when it momentarily stops at the vertex and will then fall base first. The round has only to be fired a small way off vertical for it to follow a standard trajectory and continue to the ground point first. It will then arrive at a much higher residual velocity because although the effect of gravity will be exactly the same, air resistance to the pointed bullet will be far less than to a bullet falling base first.

Regards

TonyE