Okay...
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.
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.
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.