accuracy/efficiency of machine gun fire

[PzKfW]

422 is precisely what I meant. Most non-marksmen (IE: lay shooters, or GIs from 1944) do not understand the difference, but when it is explained to them they readily agree that the concepts are distinct.

I don't think it is very important to the issue at hand other than to say that the MG fire sweeping across the action square(s) which the target squad occupies, as shown in the OP, is likely in effect a game modeling of dispersion. Whether you want to call it intra-burst or inter-burst (it looks like sweeping fire to me).

I also counted the rate of fire for the HMG in the last twenty seconds of the 2nd video in the original post. There was seven bursts in twenty seconds. That makes each minute, assuming no belt changes, etc, have 21 bursts. Each burst was around 5 rounds. That means that 105rds/min is the maximum firing rate of an HMG 42, on a stationary squad, in the open, at 200m distance, with no interruptions.

Funnily enough, the opening of that video in the OP has a belt change. Guess how long that takes? 34 seconds. Even with a barrel change, that is ridiculous. A barrel change takes maybe 10 seconds. Maybe. As shown, at a rather leisurely rate, in this video at 25 seconds into it

- 6 seconds, taking your time. The effective ROF for the HMG in the video, for the entire minute and 9 seconds, was 9 bursts, at 5 rounds each. That is less than 50rds/min.

Also, the end of the video has what sounds like the HMG squad pausing their fire to reload... again. (Remember, they had just reloaded at the beginning of the video). Which, if true, means that the game is modeling MG belts of only 50rds, not 250.

[JonS]

I think whether precision is being used to refer to precision or accuracy, and accuracy to accuracy or precision, is kind of important. For example:

I don't think it is very important to the issue at hand other than to say that the MG fire sweeping across the action square(s) which the target squad occupies, as shown in the OP, is likely in effect a game modeling of dispersion

Sure, but is the dispersion being modeled in the game that the gun can't hit the broad side of a barn, or that the gunner is deliberately spreading fire around? The net result is the same, I guess, but when you're suggesting changes the difference matters. Are the guys in the Intel Bulletin talking about the MG34/42 as if it were a shotgun or a sniper rifle?

I'm reasonably confident that almost all US/UK/Ger soldiers who passed basic in the 1940s would have had at least some exposure to the twin concepts.

I'm going to stick with precision being used to mean precision. And accuracy being used to mean accuracy.

the end of the video has what sounds like the HMG squad pausing their fire to reload... again. (Remember, they had just reloaded at the beginning of the video).

I have a sneaking suspicion - based on not very much - that remaining ammo is expressed as a probability. By which I mean; the remaining ammo in all weapons is not modelled explicitly. Instead, each time a weapon is fired there is a %age roll based on the size of the magazine or belt. For the SMLE (10 round magazine), that would mean that for each round fired there's a 10% chance that it is deemed to be the last round, and then the reloading animation kicks in. For the MG34/42 with a 250 round belt, it means that there's a 0.4% chance that each round fired is deemed to be the last one.

Which, if I'm right, means that weapons have a chance of vastly exceeding their actual magazine/belt capability, but on average they'll be reloading after firing half a magazine/belt.

I think. Based on a few passing observations.

Across any battle involving more than a platoon that's probably a reasonable abstraction, which'd save quite a bit of saving and fetching. When you're closely following a single weapon it probably looks a bit stupid.

[PzKfW]

FROM JonS

I think whether precision is being used to refer to precision or accuracy, and accuracy to accuracy or precision, is kind of important.

I meant, their accuracy could be either precision or dispersion, but when referring to dispersion specifically, they would have to mean precision.... must be the long hours... sorry for confusion/frustration

Ideally, the fire from the MG34/42 in CM would be very precise but not very accurate, using scientific terminology as in posted graphic.

That would mean that the gun itself was capable of great precision, but when it was aimed at something, would direct fire away from the "point of aim", IE: was not accurate. The origin of this could be:

1.Sights

2.Operator ineptitude (most likely)

Keeping in mind that great precision IS NOT a desirable characteristic in a machinegun, this would explain what the GIs meant when they said:

The

Germans had a machine gun on each side of the house

and riflemen inside it. When they opened up, we

dropped down, wriggled out of the dispersion areas

as fast as we could, and then ran. All 12 of us got

away without a scratch. Why the riflemen didn't get

us I don't know. However, I've heard a great many

U. S. soldiers comment that German rifle fire is not

as accurate as ours.

The GI here is talking about bolt-action rifle fire he says was not accurate (it was either not precise, or not accurate, or both) and being pinned by MG42 area fire that we know has "small dispersion" (it WAS accurately aimed, at least at this point, but also VERY precise, and easy to escape).

When a target hits the dirt, the gunner doesn't necessarily see the target anymore. The gunner will continue to fire at the area the target was last seen in to keep their heads down (or to try and hit them through cover, etc). If the precision of the weapon is great, not many rounds will deviate from the aimed at area. That means that the GIs could easily "wriggle out of the (small) dispersion (aka VERY PRECISELY HIT) area". Presumably on their bellies. But if the sights show the gun is shooting at the correct area, and the gun is actually shooting 20m to the left, that is bad ACCURACY, and would affect the first burst or two coming from the weapon, until the gunner had walked rounds onto target.

[akd]

It is also possible (likely, even) that in many of these cases the MG gunner never saw the target and was firing along a fixed line. This would be an example of ineffective employment (poor siting, lack of traversing fire) that has nothing to with the nationality or type of machine gun.

[PzKfW]

And again,

I'd like to add, too, that our Browning automatic

rifle is accurate at a greater range than the German

MG 42

this is a questionable remark when we consider accuracy and precision, and what they mean, rather than the laymans simple "accurate".

More than likely, he is saying the BAR is both accurate (has good operators in general, quality of assembly, and sights) and precise (good ammunition, materials, and design).

For example, I could have a rifle and it might shoot two shots into two places, 6' apart, when I aim at a single target. As long as the average impact location (IE, right in-between where the two shots actually hit) is at the same spot as the sights were aiming when I shot the rifle, the rifle would be considered accurate. I could have a very precise rifle that shot all shots into the same hole, but the hole was always 6' to the left of the target I was shooting at. That would be an example of a very precise rifle.

Ideally, for a rifle, you want both precision AND accuracy. For a MG, you want ACCURACY, but NOT precision. The GIs only spoke of the MG42 as having "small dispersion", IE: great precision. They spoke to its accuracy (in the document) as being less than the BAR. That makes sense considering the quality of assembly of the BAR and the operators using it.

"Their light machine-gun fire is harassing as hell,

but I don't think much @f its accuracy

Again, vague. But since we know it has "small dispersion" IE: great precision, that can only mean in this context they were talking about accuracy.

So in general, MG34/42, very precise, not very accurate (could be operator error however - we'll never know until someone chimes in who's shot one).

[PzKfW]

It is also possible that in many of these cases the MG gunner never saw the target and was firing along a fixed line. This would be an example of ineffective employment that has nothing to with the nationality or type of machine gun.

This is absolutely true. You are referring to suppressive fire from a MG, directed from different, closer troops? As in, "lay down some suppressive fire at those trees on that ridge"?

[Killkess]

It is also possible (likely, even)

that in many of these cases the MG gunner never saw the target and was firing along a fixed line. This would be an example of ineffective employment (poor siting, lack of traversing fire) that has nothing to with the nationality or type of machine gun.

You speak about the cases in the reports or in the videos i´ve posted? For the latter i dont think that this is true because in most cases I´ve used covered arcs and not a direct fire command. That way each soldier only opens up if he identifies a target.

[JonS]

I don't know why you think that rounds from the MG34/42 didn't go where they were pointed (i.e., that the MG was inaccurate)? The GI comments should probably be read as if they thought they were the target, which is an insupportable assumption. That the MG34/42 missed them doesn't - necessarily - mean the weapon was therefore inaccurate. It could just mean it wasn't pointed at them (either pointed at a different target, or as akd points out pointed at no particular target at all).

[JonS]

This is absolutely true. You are referring to suppressive fire from a MG, directed from different, closer troops? As in, "lay down some suppressive fire at those trees on that ridge"?

Yep, and it could be either offensive or defensive.

I don't agree that firing on fixed lines was evidence of "ineffective employment" though. Enfilade, defilade, reverse slope, indirect fire, FPF, are all really good reasons to use fixed lines without ever seeing the target.

[akd]

I did not mean all fixed fire was ineffective, but that it was ineffective against the GIs contributing to the AARs. If it were effective, they would not have both been able to avoid the fire and advance against the position.

[PzKfW]

Re: precision - I don't know whether you're agreeing with me or not now :confused: That dictionary definition perfectly matches the way 'precise' is used in your diagrams. 'Precise' says nothing about whether the target was hit, but everything about the spread between rounds. It also matches my understanding of dispersion/precision/consistency.

Most shooters I know understand the twin concepts of accuracy and precision, rather than just recognising a single attribute of 'accuracy'.

Could you check that what you wrote in #422 is what you meant to say?

inter/intra: noted and corrected.

Yeah, actually 422 the order is reversed. I'm off to bed now, frustrated

[JonS]

I did not mean all fixed fire was ineffective, but that it was ineffective against the GIs contributing to the AARs. If it were effective, they would not have both been able to avoid the fire and advance against the position.

Ah, gotcha. Yes, good point.

[John Kettler]

This has now become an even more exciting discussion. I knew nothing about special German ammo slings and such, but I see, once again, that what I've lobbied for time and again, hand carts, figure prominently in discussions at this tactical level. The U.S. had them, as did the British. This can be readily verified by resort to the online version of the STANDARD CATALOGUE OF ORDNANCE ITEMS, Vol. 1. In my view, we're trying to schlep heavy loads around the battlefield--without what was specifically provided to make that possible in the first place.

I find the discussion of the living history aspects of handling German MGs to be most illuminating and am having no problem following the argument. What I am having a problem with is chasing down footage of usable length from which I can see what the Germans did in bringing an MG into and out of action and particularly, moving an HMG. I have seen some guys with ammo cans scurrying forward as part of an infantry squad, but all the HMG footage viewed so far is with the gun emplaced and ripping away. I had hopes for the vids called German Infantry Tactics, but through an error by EvilFingers, the poster, no less than 3 of 5 are the same one!

Regards,

John Kettler

[John Kettler]

Since there has been direct discussion of MG-34 and MG-42 narrow cones of fire, I thought the two pics here might be useful. One's of an LMG firing, the other an HMG firing, the latter evidently doing a bit of traversing fire. Night shots, so tracer shows what's happening.

http://pictureshistory.blogspot.com/2010/11/wehrmacht-german-soldiers-rare-images.html

Regards,

John Kettler

[PzKfW]

[JasonC]

I think we are pretty deep in the weeds, but in case anyone doesn't know the obvious here...

Nobody cares about accuracy if they can get precision because getting accuracy once you have precision is a simple matter of dialing in windage and elevation adjustments a few clicks on the gun's sights. If your shot groups are all over the place that won't help.

The accuracy of the weapons themselves is much, much higher than the accuracy of the shooters of those weapons. At any range, even the shortest, the biggest single contributor to the spread of impact points is simply the motion of the gun under the shooter's hand control. Shot groups are vastly tighter if you put the gun in a vise. You just can't aim it that way. The contribution of the weapon's own imprecision is typically only about one fifth the observed spread, even using supports, bipods, prone position, telescopic sights, etc. For standing unsupported more like 10 times. Training can cut those figures, but not to the imprecision of the weapons themselves.

The biggest difference between a good shooter and a poor one is simply how steady they hold the gun through the aim and fire process.

Heavy machineguns have the same issues plus lots of movement brought on by the weapon recoil. To overcome it they use things like locking screws to allow traverse only in one desired plane of variation for the fire - and also just rely on throwing enough lead to not care very much.

The reason machineguns outrange rifles is that the method of throwing lots of lead and not caring very much dominates trying to hold a rifle real, real steady, for about 99 out of 100 shooters. Their inherent precision is lower not higher, and they buck around more not less. But most shooters cannot get anything close to the theoretical accuracy of a full caliber rifle, especially using just iron sights and shooting without supports. A weapon that can hit precisely at 800 yards in expert hands will be lucky to actually hit a decent portion of the time at a quarter of that distance, and mostly won't come close at half that distance. Purely because the man firing it cannot physically hold it steady enough.

This is obvious to anyone who actually shoots the things. But given the discussion, it sounded like some could benefit from reading it...

[dieseltaylor]

PzKFW - unfortunately the Intelligence Bulletins seem to me to be higher on morale boosting than on fact. Quite understandably but not much use in sorting fact from fiction.

With regard to accuracy and killing the War Department did do some paper on unaimed fire versus aimed. To extrapolate to longer range the natural dispersion plus a very small movement by the gunner would provide traversing fire - pinpoint accuracy not really being a benefit.

Incidentally the benefit of tracer even at short ranges is interesting and unexpectedly high.

"WO 291/473 Performance of bullet weapons.

On the matter of relative rate-of-fire of the Bren and MG-42, this paper says "...the advantages of the German gun over the Bren are due almost entirely to the belt feed rather than to the cyclic rate."

A trial was conducted to find out, for closely-spaced standing targets, whether "traversing fire" – traversing the gun over an arc without aiming at individual targets – was superior to "service bursts", that is, firing short aimed bursts at individual targets, with the Bren gun. The results tabulated here show the expected number of casualties per 30 seconds' firing:

Range (yds) Spacing in feet Service bursts Traversing fire

100 4 9 16

100 8 5 8

200 4 8 12

200 8 5 7

Another trial concerned the relative accuracy of the Bren fired from the hip using ball and tracer ammunition. Firing at fixed targets at 35 yds and moving targets at 17 yds, an improvement averaging 24% was found firing tracer rather than ball."

......

[Fernando]

I think we are pretty deep in the weeds, but in case anyone doesn't know the obvious here...

Nobody cares about accuracy if they can get precision because getting accuracy once you have precision is a simple matter of dialing in windage and elevation adjustments a few clicks on the gun's sights. If your shot groups are all over the place that won't help.

The accuracy of the weapons themselves is much, much higher than the accuracy of the shooters of those weapons. At any range, even the shortest, the biggest single contributor to the spread of impact points is simply the motion of the gun under the shooter's hand control. Shot groups are vastly tighter if you put the gun in a vise. You just can't aim it that way. The contribution of the weapon's own imprecision is typically only about one fifth the observed spread, even using supports, bipods, prone position, telescopic sights, etc. For standing unsupported more like 10 times. Training can cut those figures, but not to the imprecision of the weapons themselves.

The biggest difference between a good shooter and a poor one is simply how steady they hold the gun through the aim and fire process.

Heavy machineguns have the same issues plus lots of movement brought on by the weapon recoil. To overcome it they use things like locking screws to allow traverse only in one desired plane of variation for the fire - and also just rely on throwing enough lead to not care very much.

The reason machineguns outrange rifles is that the method of throwing lots of lead and not caring very much dominates trying to hold a rifle real, real steady, for about 99 out of 100 shooters. Their inherent precision is lower not higher, and they buck around more not less. But most shooters cannot get anything close to the theoretical accuracy of a full caliber rifle, especially using just iron sights and shooting without supports. A weapon that can hit precisely at 800 yards in expert hands will be lucky to actually hit a decent portion of the time at a quarter of that distance, and mostly won't come close at half that distance. Purely because the man firing it cannot physically hold it steady enough.

This is obvious to anyone who actually shoots the things. But given the discussion, it sounded like some could benefit from reading it...

Some info I put in the forums. You can use it as you wish:

In the Beta forum I wrote:

Page 336 of Myrvang's MG34-MG42 book:

When firing a machinegun, no matter how securely it is mounted or how experienced the operator, the projectiles will not hit the exact same spot. The variations are determined by a number of factors including the rigidness of the mount, the experience of the gunner, and the uniformity of the ammunition. Each projectile has its own trajectory, and a combination of all of the trajectories in a single burst is called "cone of fire". The cone of fire is determined by the trajectory and also sideways dispersion of each individual round. This is international military nomenclature for the machinegunner.

Somewhere out in the field, the cone of fire hits the ground in a elliptical pattern, which is called the "beaten zone". The farther away the target, the shorter and wider the beaten zone becomes.

If the ground is not flat -which it rarely is- the slope must be considered. Ground that slopes away from the machinegun makes the zone longer, while firing onto rising slope makes the beaten zone shorter. The "centre of impact" is the centre point of the beaten zone.

"Grazing fire" is a term used to describe the fire achieved when the centre of the cone of fire does not rise more than 180 cm (6') above the ground -the height of a standing man. A rifle-calibre machinegun can achieve this on even ground (or ground that slopes but with the machinegun level with the ground) up to about 800 metres.

"Searching fire" is used to lengthen the beaten zone to cover a greater area. On most machineguns the T&E (Traverse and Elevation) mechanism must be adjusted manually for each burst, but with the automatic searching fire unit of the MG Lafette, this is not necessary.

The longer the distance between the machinegun and the target area, the wider and shorter the beaten zone. This is due to the trajectory of the projectiles. When firing at long ranges the trajectory needs to be higher, and the projectiles are coming down at a steeper angle onto the target area at extreme ranges.

"Fixed fire", or "aimed fire", is when the target area can be covered with the beaten zone without using the searching fire mechanism.

AFAIK no other country put in service a tripod as sophisticated as the WWII German Lafette. It has a cradle with integrated recoild system and an automatic searching fire device which allowed to select different beaten areas.

Here

http://www.battlefront.com/community/showpost.php?p=1387314&postcount=47

I wrote:

The HMG version had a searching fire unit (Einstellring für Tiefenfeuer) installed on the Lafette. When the cradle recoiled, the actuator activated the searching fire device. It elevated the unit with the first five round then depressed it with the next four rounds in a cycle that went on for the whole burst. That way the area covered by the MG fire increased improving the suppression effect and enlarging the beaten area, so fire didn't concentrate in a too small area. If you didn't want searching fire then you just had to set the searching fire device at 0. Depending on range and desired beaten zone, you could set different values.

I also wrote in the Beta forum:

According to page 348, the diameter of a cone of fire at 600 without searching fire mechanism activated is 2,8m. Thats for a depth of 100 +/- 50 meters.

Next page gives the full and effective depths of Beaten Zone (in metres) with and withouth Searching Fire for a flat terrain:

For 600 meters (F = Full, E = Effective, 100 Tief means Searching Fire device set to 100 meters depth, which was the norm, while 200 Tief means set for 200 meters):

No searching fire: 380(F), 160 (E)

100 Tief: 480 (F), 175 (E)

200 Tief: 580 (F), 220 (E)

As a side note the searching fire mechanism works better for longer distances:

1,200 meters:

No SF: 180(F), 75 (E)

100 Tief: 280 (F), 100 (E)

200 Tief: 380 (F), 155 (E)

2,000 meters:

No SF: 150(F), 65 (E)

100 Tief: 250 (F), 100 (E)

200 Tief: 350 (F), 150 (E)

3,000 meters:

No SF: 200 (F), 80 (E)

100 Tief: 300 (F), 110 (E)

200 Tief: 400 (F), 160 (E)

At 600 meters the effective depth of the beaten zone is 160 meters.

The cone of fire diameter is at least 2.8 meters, so the smallest effectively covered area is about 2.8x160 = 448 m2.

10 men x 0.6 m2 = 6 m2

Probability of hitting a man is 6/448 or roughly 1/75

If you fire 100 rounds (about 2-4 bursts for a sMG) and about 75% fall inside the beaten zone, it means you should hit 1 man.

BTW that is one of the reasons Germans wanted high ROFs: They allowed them to put in a given area in the same time twice as much bullets than any other nationality thus maximizing the chances of hitting someone there and supressing the whole enemy unit. I think it is a sound concept.

I also wrote:

From Myrvang's "MG-34, MG-42 " book (page 351-352):

The following have been taken from the original manuals for the heavy machinegun:

The cone of fire from the Lafette-mounted MG is best use in this manner:

Fixed fire, withouth searching fire under good conditions at easily defined targets at a maximum range of 800 metres when the observations is easily made.

With searching fire against narrow targets to 1,200 metres

With searching fire and the traverse stops adjusted against narrow targets over 1,200 metres, plus all distances in poor weather conditions-darkness, fog and gas.

Targets within 1,500 metres will be eliminated easily.

Targets within 2,500 metres will be engaged with a great level of success

Targets beyond 2,500 metres will be kept down when engaged.

When firinbg at covered targets or targets in fortified positions, these targets may only be kept down. The lenght of the burst should be kept at a maximum of 60-70 rounds. Longer bursts should only be used if the impacts on the target are easily observed and the results are unquestionable....

.....The original German manual HDv73, Schiessvorschrift für das Schwere Maschinengewehr, states that the way to calculate the effectiveness of fire from the MG Lafette is as follows:

...One MG at 2,100 metres with a target area of 100 metres searching fire and 150 metres traverse fire with 100 prone infantrymen in the target area, wich makes a target area of 15,000 m2, every infantryman beign 0,6 m2, for a total of 60 m2.

60 divided by 15,000 is 60/15,000, or 1/250 chance of a hit, and as some of the cone of fire misses the intended target area, only 75% of the shots will be counted.

To make a long story short, out of 1,000 rounds fired, the expected number of hits will be 3.

That's some info I had on hand. Use it as you wish.

[JasonC]

dt - useful and believable. Note how short the ranges are, however. Extremely short for HMG style ranged fire. And the hip fire numbers are pistol ranges...

[JasonC]

"...in the same time"

Operative clause. ROF does not create bullets or make them any lighter, and firing time simply is not scarce. The only benefit left is getting the time of fire to coincide with brief intervals of target exposure. And that simply is not present with a continually exposed target.

With a continually exposed target the relevant measure is expected hits *per round fired*, not per unit time. Because it is rounds available, not firing time available, that controls total fire delivered in that case. If you throw ammo twice as fast but get 15% fewer hits per round, then for a snap target you are ahead 70% - but for a sustained target you are simply behind 15%, and the ROF itself is just useless.

The battle utility of ROF thus turns on how common snap fire is compared to sustained targets. It is emphatically not a one sided, clear gain.

There is a reason essentially no modern military goes for ROFs as high as the MG42, and it is not any inability to match or exceed it in tech specs.

[dieseltaylor]

JasonC - I agree the ranges are not what one would expect and the targets a laugh but the concept of targeting versus traversing is interesting. And given the speed of a bullet out to say a 1000 metres against reaction times perhaps a patrol would be upright .....

The Bren range is ludicrously short and one at which you would think the eye naturally would be sufficient - however such an improvment at this short range really makes the case for tracer as a sensible addition to a magazine. Shame the amount of tracer was not included either left out by WD or JD Salt.

Fernando - thank you for all your posts. Quite an antidote to the YouTube video of the US Army comparing the various weapons. : )

[dieseltaylor]

There is a reason essentially no modern military goes for ROFs as high as the MG42, and it is not any inability to match or exceed it in tech specs.

Is it something to do with arming yourself for the last war is a miltary tradition?

It makes me smile when you consider the Western Allies have found that their rifles are too short-ranged for the current theatre and had to bring old stock back into action ..

" Not long after U.S. forces invaded Afghanistan, al-Qaeda and its Taliban allies came to realize that America’s 5.56x45 mm NATO infantry rifles lost most of their lethality beyond 500 meters. Demonstrating their adaptability, the insurgents exploited Afghanistan’s sprawling valleys and distant mountainsides to seek engagements beyond the M16’s and M4’s effective ranges."

And yet the M14 was a bust in Vietnam. : )

I am not in aposition to say whether the Germans were right or wrong in their preference for a lot of bullets in a short time. However n terms of practical experience they had more than most with the Spanish Civil War giving them a chance to get an early insight into modern warfare.

[Fernando]

I have read there were two reasons for high ROF:

1. AA fire is much more effective. At the time the MG was designed it was a must for an "universal" MG. AFAIK today it is not.

2. A battlefield with more mobile targets exposed for a short time was expected, so it was desirable to be able to put as many bullets in an area as the MG could deliver before the enemy target could evade your fire.

If you man a camouflaged HMG then you target an enemy platoon 600 m away, then you need 6,6 seconds of continuous fire in order to put 50 rounds in the beaten zone (about 16 rounds, 25%, will miss it out of 66 fired) with a 600 rounds/minute ROF. If your ROF is 1,200 rounds/minute then you need 3,3 seconds to put 50 rounds in the beaten zone. It cuts in half the time available to your enemy for a quick reaction.

[dieseltaylor]

Darn good reasons Fernando. I am rather disgusted with myself for forgetting about airplanes. Experience shows as planes got much faster and more robust HMG's were unlikely to cause fatal damage. However at the beginning of the war it no doubt seemed a good idea.

[ArgusEye]

From what I remember, the ROF for the MG42 was decided upon by observing that the variable ROF on the MG34 with that feature was always turned up to the maximum by the soldiers in the field. There was a requirement by the Waffenamt in 1937 that machine gun ROF should be increased due to experiences in the field, and again in 1941. The reason for which would be interesting to find.

There are three aspects to deciding how effective machine gunnery is. First is how many casualties it makes. High ROF has advantages and disadvantages there. You catch the upright squad before they can hug the ground with more bullets. On the other hand, you burn through your ammo quicker. I have yet to see real research into this, although it does make sense.

The second aspect is suppression. With a steady dunka-dunka-dunka, you can keep going a lot longer with your ammo supply than with a fast crrrack! The suppression by the MG42 wasn't so much the bullets flying around you the whole time, but more the realization that if you showed your head, somebody would try to saw it off. Whether that is more, less, or equally useful is up for debate.

The third aspect is how the machine gunner experiences the whole affair. If the machine gunner feels more confident in a faster shooting gun, he will stick to it longer. If he is comfortable that a one-second burst has hosed down a target sufficiently, so that he doesn't need to keep focusing on it, he might be able to keep more targets occupied. The machine gun is not only beating the morale of the enemy down, it's raising the morale of your own guys.