accuracy/efficiency of machine gun fire

[Killkess]

If the gunner panics, with a 1400rpm fire rate, the mg42 will very easily melt the barrel from over firing. As will any air cooled MG.

"IRL", as you say, barrels DO melt. Just not from two or three 10 round bursts.

From my pov, if the barrel would begin to melt, i think the bullet will get stuck somewhere in the barrel and all pressure goes back into the champer. This would almost certainly destroy the whole mechanism, maybe even wounding the operator and as a result u dont have to change the barrel at all.

Before melting shouldnt the barrel first begin to loose its straighness and capability to withstand the pressures involved?

[womble]

I thought the point was quite clearly made, but let me spell it out for you.

If the gunner panics, with a 1400rpm fire rate, the mg42 will very easily melt the barrel from over firing.

Not unless the gunner's assistant has linked more belts than is customary, and keeps linking them when the weapon goes into runaway mode. At >1400rpm it eats 50 round belts faster than even the best assistant can join 'em on the end. That is, if it doesn't jam first.

[sburke]

Are you saying you have?

Black Friday at Walmart/Best Buy etc!!!!

[PzKfW]

From my pov, if the barrel would begin to melt, i think the bullet will get stuck somewhere in the barrel and all pressure goes back into the champer. This would almost certainly destroy the whole mechanism, maybe even wounding the operator and as a result u dont have to change the barrel at all.

Before melting shouldnt the barrel first begin to loose its straighness and capability to withstand the pressures involved?

They don't lose the ability to withstand pressures and kaboom, but they will droop under their own weight and ultimately jam from the bolt welding to the face of the chamber.

[PzKfW]

Not unless the gunner's assistant has linked more belts than is customary, and keeps linking them when the weapon goes into runaway mode. At >1400rpm it eats 50 round belts faster than even the best assistant can join 'em on the end. That is, if it doesn't jam first.

note that the cyclic rate of fire on the m60 is 500 to 650 rds/min

[PzKfW]

Not unless the gunner's assistant has linked more belts than is customary, and keeps linking them when the weapon goes into runaway mode. At >1400rpm it eats 50 round belts faster than even the best assistant can join 'em on the end. That is, if it doesn't jam first.

Barrel heat is cumulative and increases much faster from firing than the cooling from airflow can reduce it. That's why water cooled mgs like the vickers were designed. Runaway mode/slamfires would more likely occur from auto-cookoff of the round by the chamber heat. Since this is the area of the mechanism that has the most metal around it, and thus the most heat sinking, it would occur after the thinner portion of the barrel had already begun to sag (melting).

[Killkess]

What on earth is paradoxical about that? Do you not realise that this is basic reason why infantry don't still advance shoulder to shoulder in three ranks, why infantry tactics underwent an absolute revolution between 1914 and 1918, and is the genesis of the phrase "the empty battlefield"?

I just want to come back to this point because it may also be relevant for the HE argument which started lately in this thread.

I guess one can not argue if artillery caused more cassualties compared to small arms fire or not. But what i want to point out is that this was not the case because artillery was that much more lethal. Due to the lethality of small arms the once target rich battlefield changed into a mostly empty one. The enemy soldiers used extensive cover and or concealment to protect themselfs against the modern hazards.

The only mean, with which the enemy was still reachable, is by indirect fire. And thats is one of the reasons why u will find more cassualties to artillery/mortar... the average grunt doenst expose himself to direct small arms fire very often, but can´t avoid inderect fire to the same degree.

And this leads to the conclusion that comparing average RL statistics to "exceptional situation" like storming a HMG headon isnt very usefull.

[PzKfW]

Black Friday at Walmart/Best Buy etc!!!!

You should have seen them going after the shoes.... but it reminded more of "the walking dead" than "ostfront".

[Killkess]

...and thus the most heat sinking, it would occur after the thinner portion of the barrel had already begun to sag (melting).

OK, do one already speak about a melting process if the barrel begins to bend? For me melting begins with getting something liquid.

[PzKfW]

OK, do one already speak about a melting process if the barrel begins to bend? For me melting begins with getting something liquid.

For a barrel, yes

[PzKfW]

Not unless the gunner's assistant has linked more belts than is customary, and keeps linking them when the weapon goes into runaway mode. At >1400rpm it eats 50 round belts faster than even the best assistant can join 'em on the end. That is, if it doesn't jam first.

http://www.youtube.com/watch?v=AwW31u6wYvE Note the barrel smoking at the end.

[c3k]

Oil is used as a rust-protectorant on many weapons. Smoking barrels do not indicate the barrel is anywhere near a melting point. (I did not watch the linked video.)

[PzKfW]

I am not saying it is. It is an indicator of heat, however. After what, 50rds?

[JonS]

Runaway mode/slamfires would more likely occur from auto-cookoff of the round by the chamber heat. Since this is the area of the mechanism that has the most metal around it, and thus the most heat sinking

And that's presumably why a lot of MGs (incl the MG42) have an 'open bolt' design. It's harder to have a cook off when there's no round in the chamber.

Can we just clarify something though. You attempted to ridicule Apocal on the basis that he'd "never seen a human wave." Have you "seen a human wave", or are you just pulling things out of a dark place?

Also, I'm curious what tactical advantage you see accruing to the machine gunner who lets his barrel melt, rather than taking the few seconds to swap it out.

[JonS]

I am not saying it is. It is an indicator of heat, however. After what, 50rds?

Heat shimmer is probably a more useful indicator.

Better yet; the end of a 200-rnd belt is an excellent indicator that it's time to change.

[PzKfW]

Regardless of bolt design the chamber heat, heat sink and welding point remains. Especially on a roller locker mechanism like the mg42 or g3.

I was not trying to ridicule but rather make a point, since a very common sense idea, namely, that guys who panic under extreme duress are not likely to follow protocol, was being attacked. This is a underpinning of the entire CM game. I believe he said that they never melted but were always swapped out before that point.

Bs. Guys panicked. Barrels melted. Especially with a rapid rof mg like the mg42. Happened and to say it didn't or couldn't is blatant disregard for realism. I never said that DESIGN intentions were to let it melt. Obviously not. But in a human wave attack, maybe you just forget, hmm? It happened in Korea to the US gunners too.

There is no tactical advantage and you asking that question just illustrates you don't understand my point.

[YankeeDog]

I am not saying it is. It is an indicator of heat, however. After what, 50rds?

That's substantially more than 50rds. Over 100; probably a 200 rnd. belt.

[poesel]

FYI: at around 600°C you start to see a faint glow, between 900-1000° you get a nice orange, 1200° is a bright yellow. When you see sparks and the yellow turns whitish you are close to melting (~1400°+).

That's for 'normal', solid steel. YMMV for other types of steel.

[PzKfW]

I agree. I think that the gun was under most circumstances fired with a reasonable Rof and at the end of the belt had the barrel quick changed.

Heat shimmer is probably a more useful indicator.

Better yet; the end of a 200-rnd belt is an excellent indicator that it's time to change.

[PzKfW]

That's substantially more than 50rds. Over 100; probably a 200 rnd. belt.

Yes. Well, the section of the belt we can see at the beginning is 20ish rounds. I should have said 75-100rds to be safe.

[JasonC]

The standard was to fire 250 rounds and change the barrel, cycling through at least 3 of the things to maximize cooling time.

German training documents give the sustained ROF of the MG42 in LMG form at 250 rounds per minute, only 150 for the MG34. In HMG configuration, 500 and 300 respectively. And those are with changes.

Well maintained guns with modern ammo can fire 700 rounds without a barrel change without jamming, but that would be exceptional in WW II conditions. The ammo was much, much worse, and all the barrels would already have considerably greater wear.

Period AGs report that it was entirely normal for the last bullet before a change to be found jammed in the breech, and they'd spend half their time hammering them out with a rod and mallet. The Germans suffered serious material shortages in the second half of the war, and this meant their ammo was often not copper jacketed, but plain steel, which was lubed to prevent rust. The lube would burn off when the gun got too hot, resulting in higher friction and more frequent stoppages.

The normal thing that happens with an overheated gun is that first, accuracy at range drops significantly, and second, the gun jams outright. The size of the bore is changing with the temperature, the internal surface can heat unevenly, "windage" can arise and slippage on the rifling. At higher temps for longer period the internal surface can flake, and the bullets are chipping pieces out of bore side here or there on their trip out, which is progressively wrecking the barrel as well as degrading accuracy.

You get outright stoppages when the barrel has deformed enough from differential expansion from the heat that it "grips" the bullet, or when the torque on the bullet (from not flying straight, flake kinks, etc) deforms it against the bore side, and that then blocks up the barrel. High enough heat can also weaken the barrel walls, but the previous is likely to happen first. If the gunner detects the stoppage fast enough he can let up and not destroy the gun by firing into the blocked barrel. This is obviously much harder to do in a 20 round per second cyclic rate gun than at a third or half that cyclic rate - the gunner has a twentieth of a second to get off the trigger or he will fire a second bullet into the blocked barrel.

Any way it is sliced, it is dangerous to run a gun too hot too long. They normally could not be fed even at the sustainable rates given above for very long - battles lasted hours not 10 minutes - but certainly could not be fired at cyclic rate continually. No air cooled MG could. Water cooled and starting from a slower cyclic rate, around 450 rpm, that could be sustained indefinitely. But not air cooled 1200 rpm, not even with barrel changes.

In game terms, if a gun truly "went hot" on operator panic, it would jam up in under a minute.

[YankeeDog]

Yes. Well, the section of the belt we can see at the beginning is 20ish rounds. I should have said 75-100rds to be safe.

You can see 23 rounds showing on frame at the start. I counted. Plus one or two under the feed plate you can't see. If you watch closely, you'll see the empty belt coming out the other side, descending and falling completely out the bottom of the frame, well before we first see the last bullet on the belt come into the frame on the other side. So I'm confident it's at least 100 rounds, and 200 wouldn't surprise me.

The MG42 is an ammo munching beast. 50 rounds = 2.5 seconds of trigger down time. That vid really helps you appreciate why most modern GPMG designs have gone with a significantly lower ROF.

[PzKfW]

So. That means between 8 and 9rounds fired every second, over the entire minute, for a mg42 hmg. Continuously. And that is the sustained fire rate but with breaks for barrel swaps?

Makes sense to me. And it's a far cry from the current state of affairs.

[c3k]

Heat and barrels: check the M14 acceptance tests. They fired that thing continuously with some sort of "torture test". The wooden handguards igniting from excessive barrel heating was noted (some ridiculously high round-count), but did not detract from the test since the weapon continued to fire.

I have no idea what the ignition point of walnut is, but it was exceeded where it touched the barrel.

Ken

[PzKfW]

Yup! They subsequently went to fiberglass.