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Coaxil MGs purpose?


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What was the purpose of coaxil MGs in tanks? Were they just a left over in desgin from when tanks carried little more than machine guns such as the Pz I and II?

Was their ever any training or indeed did tank designers put in coaxil MGs to help estimate range? Or was it just for keeping a tank buttoned up?

Cheers

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A co-axial MG is an alternate weapon for use when use of the main armament is not justified, or to conserve main weapon ammunition. As it has a far higher cycle rate, it is more effective against enemy infantry. Mounted as it is, with effective sights, it is an offensive weapon, as opposed to hull mounted weapons which were intended for self defense, IIRC.

If you track down rexford's latest thread on Sherman ammo, there is a reference for using the MG to range for the main gun, but this does not seem to have been standard practice.

Dedicated ranging MGs are also mounted co-axially, but tend to be of heavier calibre (eg .50cal) in order to match the trajectory of the main gun. In the Centurion and early models of the Chieftain, which both mounted a ranging MG, they also mounted a rifle calibre (7.62mm) MG co-axially, for attacking infantry.

It can also be noted that on early WWII British tanks, the turret mounted MG was considered the primary AP weapon, so no little or no provision was made for an effective HE shell - tank guns were chosen for AT capability at close range.

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Originally posted by flamingknives:

If you track down rexford's latest thread on Sherman ammo, there is a reference for using the MG to range for the main gun, but this does not seem to have been standard practice.

Ahh cheers that seems to be a thread that answers some of my questions!

Thanks

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IIRC Israelis did start using specailly designed rounds in the coax to range main guns in the 50s or 60s. Probably would not work without special rounds, as the main gun and the coax have far different ballistic properties. Before the advent of laser range finding the real issue with aim was not adusting left-right but getting the range right.

WWB

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Before the advent of laser range finding the real issue with aim was not adusting left-right but getting the range right.

Quickly, I think is the key point.

Both WWII (Hetzer, probably others) and post war (Conqueror, for certain) mounted co-incident range finders, which were adequte at least, just not quick and they needed some skill to operate.

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Actually, the term 'coaxial' is a bit of a misnomer here, as literally it means "having coincident axes". What this would mean in practice is the MG firing down the barrel of the cannon! Such was not the case. The coax MG on a tank was mounted so as to fire in parallel to the main gun, and therefore able to use the same sighting mechanism. Since, as has been mentioned, the ballistics of MG ammo are not the same as the main gun, the gunner would have had to make some adjustments in order to get accurate aim. The coax MG was used to suppress and inflict casualties on the enemy.

As an aside, it has been mentioned here and in another thread recently that the hull MG was used for self-defense only and I wonder what the source of this idea is. My notion is that on attack, the tank went in with all guns blazing. The hull MG might in fact have seen more use than the coax, since it could continue firing when the gunner was concentrating on using the main gun. Also, due to its lower location on the vehicle, it would have been somewhat better suited for grazing fire. Against that is the fact that the coax would have the advantage of better sights and be less likely to be blocked by irregularities in the ground. But I'm sure both were used whenever they had appropriate targets, both offensively and defensively (which is kind of an arbitrary distinction at this level anyway).

Michael

[ October 08, 2003, 12:48 PM: Message edited by: Michael Emrys ]

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Originally posted by flamingknives:

It can also be noted that on early WWII British tanks, the turret mounted MG was considered the primary AP weapon, so no little or no provision was made for an effective HE shell - tank guns were chosen for AT capability at close range.

Just to clarify - HE existed (and I can see no argument why a 2pdr HE shell would be less 'effective' than a US or German 37mm HE shell) for these tanks, produced in the UK. For some reason, the idiots in charge of delivering 'stuff' to the army in the western desert decided to not let them have it. They sent it to the Red Army instead.
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Originally posted by flamingknives:

</font><blockquote>quote:</font><hr /> Before the advent of laser range finding the real issue with aim was not adusting left-right but getting the range right.

Quickly, I think is the key point.

Both WWII (Hetzer, probably others) and post war (Conqueror, for certain) mounted co-incident range finders, which were adequte at least, just not quick and they needed some skill to operate. </font>

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Also, unlike the hull-mounted MGs, the coax could shoot in any direction without a need to move the vehicle. The turret mounting gave it a wider field of fire, even if the process of aiming and moving it were more cumbersome.

It would seem to me that the coax would be a more useful weapon at long range, given that it was presumably harder to move around to nearby targets. I presume that coax MGs were fixed in place and not able to move around. That would seem to limit their usefulness for close-in combat.

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Originally posted by Andreas:

They didn't have it for the Western Desert - HE in the UK was produced in response to a Russian request for some.

UK doctrine was that the 2 pdr was an AT gun and machine guns could deal with any infantry, hence there was little HE produced for the 2 pdr.

I did read somewhere that the 2 pdr AT regiments of the Aus army in Malaya had HE, sicne the countryside was supposed to be impossible for tanks they figured that HE might be necessary so the 2 pdr could be used for infantry support.

Also Australia & NZ produced 2 pdr HE for Matildas and Valentines used in the Pacific - again there was no AT role for the guns and the HE ammo was needed for bunker busting.

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Judging by the nature of the question I don't think one should underestimate the critical nature of a tank's MG armament in combat and not just for self deefnse. There are plenty of times even today when the MG is the weapon of choice over the main gun, particulary against soft targets and for suppresive fire.

Los

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The coax is magic. I have no first hand knowldege of WW2 MGs either on vehicles or dismounted, however I have seen some things of the bradley and it's 7.62mm coax, it can be used for area suppression or point targets and is effective out to 900m (laser range finder and nice magnification help here of course). Saw it used in Iraq, you can only carry so much 25mm and may not want to waste it on crunchies or soft targets so 7.62 works well. Throws recoiless rifle and RPG gunners off their aim too which can be helpful in a pinch.

not too effective in close defense(turret too slow) but thats what dismounts are for, it is nice and accurate and can be used in close (relatively speaking) proximity to civilians/ non-combatants without hurting the wrong folks (can't do that with 25mm, much bigger safety margin needed there) which despite some people's ideas was actually a really big deal over there.

[ October 08, 2003, 08:59 PM: Message edited by: EnglishRanger ]

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Actually, the term 'coaxial' is a bit of a misnomer here, as literally it means "having coincident axes". What this would mean in practice is the MG firing down the barrel of the cannon! Such was not the case.
Sorry to be picky but I disagree with your mathmatical principles there. You're probably thinking of an 'axis of rotation' which is not what's meant here. If you imagine a tank with the turret in the forward position, then we can call the 'front to back' direction the X axis. The side to side direction the Y axis and the top to bottom direction the Z axis. Just because the MG has a different position on the Y axis to the main gun doesn't mean it's not coaxial in relation to the X axis. Using the same principle of axes to the turret only it is quite correct to call the MG coaxial because it fires along the same axis as the main gun. Just because it has a different position in relation to a different spatial axis doesn't invalidate the term in this instance.

Sorry but somebody else got picky with the grammar so I thought I'd have a go at the maths ;)

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Originally posted by Rollstoy:

</font><blockquote>quote:</font><hr />Originally posted by Ant:

I am not so sure.

Personally, I would prefer co-aligned or axially parallel.

Regards,

Thomm </font>

Well I'm sure, and co-axial is perfectly valid.
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Originally posted by Ant:

Well I'm sure, and co-axial is perfectly valid.

Unfortunately, I did not find any example to back up your definition (coaxial cables, coaxial cylinders, etc. all have the same axis)

However, I found the following:

adj: having a common axis [syn: coaxal]

And from The Collins English Dictionary

1) having or mounted on a common axis

2) (Geometry) (of a set of circles) having the same radical axis

3) (Electronics) formed from, using, or connected to a coaxial cable

Regards,

Thomm

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The german co-ax MGs (at least in the Panther) were foot triggered by a pedal. Another rocker-type foot pedal would slew the turrets rotation. This would leave the gunners hands free to work the main weapon. Since the HE and MG had similar velocitys, he could work over soft targets with a double whammy. Fire several MG burts to get the range roughed in and then unleash a HE shell. The reticle looked like this:

http://www.geocities.com/Area51/Capsule/2930/pzpanther/pzpanther-Charakteristics.html

I have seen video footage of Panther turret MGs firing long tracer bursts. It appeared that the footage was shot near dusk/heavy overcast/dawn and there is no doubt that the tank is giving its position away to anyone with any LOS at all. I believe this would hold true for any MG that fires tracer.

Does anyone know if any WWII tank used water cooling for its MGs? I know that they sometimes used heavier barrels like the german tank MG34 but water cooling, using a closed vessel pump-driven system that could be roof mounted and protected, would give long burst capability. Perhaps they were viewed by designers as secondary weapons.

[ October 09, 2003, 10:30 AM: Message edited by: Mr. Tittles ]

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