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back to article Cobalt-barrel machine guns could fire full auto Hollywood style

You know in the movies, where people get hold of powerful automatic weapons - rifles or machine guns - and fire them on full automatic for ages? US troops in training carry out a barrel change on an M240B machine gun. Credit: Sgt Lindsey Bradford/US Army Goddammit Kowalski, it's supposed to come off in your hand That's quite …

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Okay...

I'm curious to know what the preformed mandrel is made from?

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Boffin

Re: Okay...

Simples

Most likely from the Cobalt alloy itself, perhaps a higher / harder grade. The article says it is hard, not impossible, to process the allow - so they could make a template.

HTH

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Re: mandrel

Parmesan cheese.

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Happy

Mandrel

Isn't a Preformed Mandrel something in the Harry Potter movies

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It's made from

the solidified juices extruded from Chuck Norris.

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Gold badge

Re: Okay...

I can see where you are coming from, but remember that the cobalt steel is soft when shoved against it and the mandrel may be allowed to cool between pressings.

I was going to suggest a ceramic for its lack of thermal expansion, but expansion might be a good thing if known and controlled. If you know that when pressed in hot cobalt steel it will expand to size x (the bore), when the whole thing cools and the mandrel shrinks again it would make extracting it from the formed barrel a rather simpler proposition.....

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Boffin

Id guess...

IOd guess some form of Tool Steel - HSS most likely. Tungsten carbide might be an option but its brittleness would probably rule it out. Would be an interesting tooling job though...

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Silver badge

Pure unobtanium

That is all

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The hardest substance in the known universe

Namely the stuff that gets baked into the corner of a rice pudding dish.

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Thumb Up

1100 Degrees

Next step, improve the oven glove they used to issue to grunts to change the barrel on the M60.

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Go

nah

just use your mates beret for the gimpy. He wont mind.

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Coat

Already been done

And available to you for the low low price of $18.95 plus S+H.

http://www.asseenontv.com/prod-pages/ove_glove.html

Then, given that this is a military procurement, add a small (say ~1500%) markup, alter the contract a few times after it is signed to further delay delivery and push up the price another 200% then cancel the whole thing when the next government gets elected.

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Unhappy

notitle

A white-hot barrel is going to be just as much a giveaway as muzzle flash.

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Go

@John Sager

"A white-hot barrel is going to be just as much a giveaway as muzzle flash."

Just because it's 1100 degrees, doesn't mean it's "white hot." Likely it will have a heat distortion effect radiating off the barrel, for sure, and just think: no need for a bayonet! Just barbecue them!

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Flame

Unlikely to be white hot

According to whackypedia, if it was a perfect black body, it'd be orangy red, usually that's a close enough approximation (1100 degrees C is about 1373 K )

But yes, still too visible

Flame, because that's what'd happen to your hand if you touched it.

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The thousands of rounds being shot won't give the position away?

If they can see the glowing barrel, they'll be able to see the thousands of rounds firing out of it well before that. A machine gunner's position is usually pretty obvious.

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Pint

Needs accessorising

With a barrel BV. Remove barrel, insert into BV, enjoy well earned brew. Anyone who adds screech powder gets cleaning duty.

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and also curious to know ...

...how do you get the mandrel out of the barrel once you're done?

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I'm sure I won't be the only one . .

to assume you just unscrew it.

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Anonymous Coward

"...how do you get the mandrel out of the barrel once you're done?"

nuke it from orbit, it's the only way.

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Boffin

RE: and also curious to know ...

Deformations tend to have 2 parts: elastic & plastic. The elastic part of the deformation revert to its original dimensions once the deforming force is removed where as plastic deformations are permanent.

Besides, one can always heat up the barrel so it expands to withdraw the mandrel.

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@Pen

You pull the mandrel and it rotates out.. hopefully you remembered to lubricate it first.

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Coat

Tempt it out with a banana

I'll get my coat.............

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Pint

First bit

of common sense I've heard all day Thank'ee, sir.

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you tap the end

taking care to point it away from your feet.

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heat up the barrel so it expands

Just a guess, but I would expect that a gun barrel designed to stay reasonably straight at 1100 degrees is not going to expend a whole lot.

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Flame

Hot as hell!

I own an MP15, which is basically a .22 calibre version of the AR15 and even a clip of 30 rounds on semi-auto will heat your barrel enough to make it uncomfortable to touch. With .223 or 5.56 NATO rounds the barrels will leave you with burns. It really is an interesting problem and I wonder if one-day they'll be able to miniature the cobalt process to make it applicable to all weapons. A flame icon cause hot barrels burn!

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Coat

A .22 semi auto barrel hot?

Try a 7mm Rem Magnum after sending down a couple of bullets 'slowly' down range.

Shoot fast enough and long enough, you end up not only with a bruised shoulder, but you can also do permanent damage to the barrel.

Mine's the shooting jacket with .300WM and Rem7 used brass in the pockets.

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And then the bullets run out

You hit the enemy with a 1,100C white-hot glowing metal rod, cool! I mean - hot!

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FAIL

Yuck

Cobalt-59 dust is poisonous and carcinogenic, so I wouldn't like to get near that barrel after it had been used !

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Silver badge

Great!

That makes it an even more effective weapon.

Just make sure the dust goes in the same direction as the bullets.

When the bullets run out, as mentioned above, whack the enemy over the head with 1100 degC stick.

This weapon is sounding better all the time!

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poisonous

Chronically poisonous, not acutely, so rather a slow assault weapon

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It's Fahrenheit, not Centigrade

As the figure of "1,100" degrees comes from an American article, it'll mean 1100 degrees F, or roughly 600 degrees C. Still pretty hot, though.

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Boffin

Title? We don' need no steenkin' title...

"Essentially the problem is that the alloy is so tough that it's difficult to cut the spiral rifling grooves down the inside of the bore, essential to make the bullet spin as it flies out of the end and so fly accurately."

Is accuracy a big issue for a weapon intended to lay suppressing fire?

If you just want to put large quantities of lead in the general area of the enemy to keep them from popping their heads up and doing Something Nasty wouldn't a smooth bore barrel do the job just fine and be a simpler solution?

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Boffin

I refuse to enoble a simple forum post!

its not just to help with accuracy, it also helps with range; that is to say a spinning round flies straighter and further than one just lobbed out the end of the barrel.

think musket versus rifle

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Go

Accurate fire is important

It was a bog-standard M2 machine gun that Carlos Hathcock used in Vietnam to set the then record for longest confirmed kill at 2500 yards. One guy on a hilltop with an accurate machine gun effectively denied the enemy the use of an entire valley floor.

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Barrel Forming

Not knowing much (read: anything) about metalworking, is there any reason why the (molten) alloy can't be poured into a barrel-shaped mould with the rifling already put in, meaning that it comes out pre-formed?

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Thumb Down

Wrong process

Barrels are forged not cast, casting creates air bubbles and weaknesses structure of the metal.

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Boffin

Armchair metallurgy

Could we do what we do with concrete then? That is, would it be possible to just vibrate the air bubbles out of the metal? Or would there still be weaknesses even if the air was purged?

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Re: Armchair metallurgy

The bubble source is completely different. In concrete the bubbles result from air entrapment, can shake them out before the concrete solidifies. In metal casting, bubbles form at the point of solidification. The molten metal contains dissolved gases that come out of solution when the metal cools and solidifies. Can be reduced by casting in a vacuum or inert gas.

I suspect casting a high-temperature alloy would pose some problems.

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Boffin

@Armchair metallurgy

Concrete doesn't have the same molecular structure as metals, as metals have a more precisely aligned structure to the atoms. A molten metal would be like the magnetic bits on a hard disk platter being scattered every which way, whereas metal that has been forged is more akin to precisely aligned bits of perpendicular-recording media. (except with metals, they're laid parallel). This is why "folded steel" makes for an extremely sharp, sound blade.

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And now I know more

And I did realise about 20 seconds submitting the post that "casting" was the word I was looking for. Oh well/

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WTF?

@ Okay...

I saw a documentary recently where a group of top military scientists successfully built a machine that took them to the centre of the Earths core to try to restart it with a couple of nuclear bombs - I think bad science or something to do with migrating birds had stopped it from spinning and generating magnetism or something. Sorry I don't have full details, but I didn't actually get to read all the facts listed in The Sun newspaper as I'd accidentaly gone on holiday at the time.

I digress though... the machine they built for this epic trip was made from a material specially designed to withstand the heat and pressures encountered at the Earths core - so I'm presuming the mandrel is made from the same stuff.

Hope that helps.

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You can guarantee...

That if the gunner or his mate doesn't have to carry a spare barrel and/or spares kit now, he'll be given another belt instead ;)

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Go

Squad Automatic Toasters

Surely this is a golden opportunity for infantry support and catering functions to be merged saving millions in defence spending.

Simply fit said 1,100 degree barrel with appropriately shaped heatsinks and you could toast waffles, bagels and even do a full-English fry-up whilst suppressing the enemy.

Come on Lewis, it would even be more carbon-neutral!

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Anonymous Coward

Vinny Leto?

Sounds more like a wise-guy to me...

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Paris Hilton

"The rifling is pressed into the bore"

But how do you get the mandrel out afterwards?

Only a perfect spiral rifling will do.

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Boffin

Your missing several other problems

Firstly, I am a soldier so I know what I am talking about.

Cobalt barrels or not, you will never be able to blaze away in full auto like they do in Hollywood for long periods of time until they sort out the recoil issue.

Firstly the assault rifle and similar. Firing on full automatic incurs a lot of recoil. So much so that by the time you have loosed off about three rounds, the recoil has made your rifle climb away from the point of aim and the rest of the rounds are useless. This is why a number of weapons such as the M16A4 and so on do not have a fully automatic mode. They have a three round burst capability as it's generally these three rounds that do anything.

It becomes a bit more useful when you consider supported weapons, or weapons that have a bipod, tripod or fixed mounting, as the recoil from these is generally supported by the ground or mounting. However while it may allow you to fire slightly longer bursts of fire, blazing through 500 rounds in one sitting still isn't going to happen. The reasons are long and complex but basically the barrel is not the only thing to heat up and simply put the gas plugs, tray feeds and even ammunition itself probably could not handle the heat build up within the breach.

Add to the fact the already mentioned factors such as ammunition conservation, not to mention preventing identification of your firing position and you can see why it's unlikely. The only benefits the cobalt barrel offers is the welcome advantage of not having to carry a second barrel or have to get the thing off after every 800 rounds (Which doesn't actually happen in a real contact, you fire until the damn thing is about to melt or you have a lull in the contact).

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Joke

I reject your thesis because...

It is clearly too logical and not sensational enough to be true. This is patently contrary to modern journalistic practices.

Next time try to include more Matrix references.

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Good God man

What do you think you are doing, coming on here and spouting off all those actual facts, its almost as if you know what you are talking about, and therefor have NO PLACE HERE.

Please reads the sitesT&C's for more details on how to make up facts, obscure the truth, or become a Fanboi, prior to posting in the forums.

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