I'm curious to know what the preformed mandrel is made from?
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 …
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.....
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.
And available to you for the low low price of $18.95 plus S+H.
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.
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!
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.
"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?
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.
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.
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.
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!
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).
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.
Room entries, assaulting enemy positions at close quarters, suppressive fire upon initial enemy contact. There are plenty of reasons to fire more than 3 rounds in a burst, and us English with the L85A2 trust our soldiers to choose when to use each fire mode, rather than restricting them to burst fire. Plus the article was mostly referring to LMGs, which as you mentioned doesn't suffer from these unsupported firing position problems.
Also they claim to have fired the weapon at 1100 degrees, so assuming this was done using a hand portable prototype, I assume they've overcome any other heat build up issues in the breach.
I don't really see what point you're trying to prove here, beyond bigging up your soldier knowhow. Which by the way really doesn't prove you know what you're talking about. I can take apart and put together a PC, but I don't know how everything works in it, and certainly couldn't claim expert knowledge on something like the PCI-E bus.
"There are plenty of reasons to fire more than 3 rounds in a burst, and us English with the L85A2 trust our soldiers to choose when to use each fire mode, rather than restricting them to burst fire."
Actually no they don't. I AM a soldier in the British Army and automatic mode on the L85 is restricted in use unless your in very specific scenarios and even then you are trained to keep your bursts to approximately 3 rounds or less to prevent recoil climb. The M16A4 was an example I gave because that specific generation model appeared long after the L85 was designed and thus incorporated more enlightened thinking and also offers a way to limit the recoil. The original M16 had full auto too. I absolutely promise you by the time you have fired about 6 rounds from the L85 your rifle is pointing a good deal higher than where you aimed and will only continue to climb.
"Also they claim to have fired the weapon at 1100 degrees, so assuming this was done using a hand portable prototype, I assume they've overcome any other heat build up issues in the breach."
That's all fine and well if they have machined a NEW weapon or re-engineered an existing weapon for the barrel. However it's not a case of simply fitting the new barrels to existing weapons as the machining tolerances are not designed for constant fire. Plus I absolutely guarantee you put a round into the breach at 1100 degrees and it WILL cook off (Regardless of whether or not it's an open or closed bolt weapon). And with the current SDSR in place, I highly doubt we will be swapping our weapons out anytime soon.
All this is aside from the fact that automatic fire in an individual weapon is rarely used because apart from being up and close and personal, it's not effective. Single aimed shots are better. As for support weapons, well in a real contact you would simply never get the opportunity to fire at the weapons full cyclic rate. Ever. Even if the weapon is mounted or bipod based.
I'm not saying they are a bad thing, not having to carry and swap out a second barrel would be a great thing (And I speak from the heart having been an LMG gunner in Afghanistan) but there is no way that they would lead to any military switching its training or operating policy to one where you can blaze away (Or "hosepipe" as we refer to it. Imagine the rounds from the barrel as a stream of water from a hose).
look here foot slogger. Some people have these things called ve-hi-cles. They have MGs on them too, oh and coax guns. And stacks of ammo in boxes.
M16A4 dont have fully auto because the yanks cant shoot for shit therefore cant be trusted with fully auto.
I think the cobalt barrels ARE intended for suppression weapons i.e. MGs rather than AWs
"there is no way that they would lead to any military switching its training or operating policy to one where you can blaze away (Or "hosepipe" as we refer to it. Imagine the rounds from the barrel as a stream of water from a hose)"
However, that ability would be very desirable for remote controlled or autonomous turrets and I can easily imagine people in Pentagon salivating at the thought of sticking Aliens2-style turrets all around the perimeter of Kandahar Air Base (or along the Mexican border) and let them blaze away at anything that moves...
"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."
On an SA80, this feature is controlled by the mechanical reliability of the weapon, magazine, and Radway Green supplied ammuntion.
Ok, so it's not the most portable, but as a machine gun it's pretty good :-)
'The weapon had a reputation for great solidity and reliability. Ian V. Hogg, in Weapons & War Machines, describes an action that took place in August, 1916, during which the British Army's 100th Company of the Machine Gun Corps fired their ten Vickers guns continuously for twelve hours. They fired a million rounds between them, using 100 new barrels, without a single breakdown. "It was this absolute foolproof reliability which endeared the Vickers to every British soldier who ever fired one."'
If you need a machine gun get a good one - stop faffing around with wannabees.
The infamous test to destruction of a Vickers machine gun when they were going out of service and people wanted to know just HOW long they would have kept going for.
Someone who was a witness to part of it told me 7 days + 7 nights, and a LOT of trucks carrying crates of ammo in, and taking away the mountain of copper that was accumulating. You don't want to know how much ammo it used, cos we paid for it. Still, on the bright side a lot of it was war stocks that had to be disposed of anyway, but...
1100 degrees of what Lewis? I'm assuming you are working with either Fahrenheit or Celsius, but it is unclear and makes a huge difference. I'm assuming that since you lifted most of the tech stuff straight from the linked article which was written by septics it must be Fahrenheit? Also the melting point of pure cobalt is only just below 1500 degrees Celsius, so presumably if the barrel got to 1100 degrees Celsius you would already be in the plastic flow region...
This is why most machine guns fire with an open bolt. That is, a round is not fed into the breech until the trigger is pulled, which releases the bolt, allowing it to close. This can be a little less accurate, because of the delay before the cartridge is fired, and the movement of the bolt mass.
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This process sounds Very similar to hammer forging (invented in 1939). That's where the barrel is drilled and honed, a mandrel is put in the center, and rotating auto hammers pound on the outside until the bore takes the rifling shape.
Anyway, this is a nice advance. From experience, I know barrels heat up Quick. This really doesn't fix that, it just allows you to get the barrel screaming hot without it failing. Of course, the weapon will have to fire from an open bolt, lest the heat alone fires the next cartridge - whether you mean too or not.
Flame, because this is hot stuff!
Flow forming is a popular way to turn mostly cylindrical things with complex profiles (especially stuff that has walls that thicken in bands or taper from one end to another) often as parts of various bits of military hardware.
The smooth force applied suggests it would give a smooth internal finish as opposed to something made by many separate hammer blows.
AFAIK the technique works very well at well above room temperature, so the metal would be softer to begin with.
Gun barrels (certainly of the .50cal variety) are *well* within the range of objects made currently with this method.
The obvious joker is if is worked hot (or even warm) unless the mandrel is withdrawn *very* quickly the barrel cools and shrink fits onto the mandrel.
In principle a clever way to make a lot of something very difficult at a reasonable price.
"the US Navy (interested in equipping its marines and SEAL frogman-commandos better)"
While the civilian leadership of the United States Marine Corps falls for administrative purposes under the US Department of the Navy, the USMC is militarily a separate armed service - they aren't 'the Navy's marines' unless you regard the suits as 'the Navy'... as a naval man yourself, Lewis, I doubt this is a precedent you'd want to set!