REAL firearms research - explosive casings

[Bill_Rights]

(Note: I considered posting this thread on the Forum area "Firearms Research", but it seems that that area is devoted to old firearms.)

The US Army has made public the information that it has been researching for a number of years, and is seeking new research on, explosive ammo casings. [Where and how the Army publicized this is not important for this thread.]

The Army, and presumably the Navy/Marines, want the dismounted soldier to be able to carry more rounds of ammunition at the same weight or the same number of rounds at less weight, leaving more weight-carrying capacity for other things.

One way to do this would be to get rid of heavy brass cartridge casings and replace them with casings that are made of, essentially, propellant. Then when the round detonated, the casing would burn along with the dedicated propellant, thus reducing the amount of dedicated, internal propellant needed and, because the propellant-based casing would be made of not-metal, the overall size and weight of the cartridge could be reduced.

Is that cool, or what?

And, what if the primer could be replaced by something like a spark plug? Then the whole dang thing would vaporize and there would be nothing to extract. No more FTEs! Much, much faster rep rate in full-auto fire.

This whole concept, if proven workable, might be an equivalent advance as going from muzzle-loaders to cartridge-based firearms. Don't you think?

 

[Special_K]

The design has already been implemented and tried. The problem is that the brass case takes a lot of heat from the chamber with it when ejected. The designs built up a lot (A LOT) extra heat without that heat sink and things were not going so well.

http://en.wikipedia.org/wiki/Caseless_ammunition

 

[Palehorseman]

I think years ago even the Daisy Airgun company made .22 caseless ammo, and it didn't work out too well.

 

[Sunray]

HK tried caseless ammo, long ago. It didn't work. 1960's or '70's technology, as I recall.
Korean vintage 105mm recoiless rifles used an almost casing that would burn along with the propellant. I suspect the whole issue is a size and weight thing.
"...replaced by something like a spark plug?..." That's been done. Electrically fired 20mm Vulcan guns.

 

[Deus Machina]

Possible, and I think it will crop up... probably three or four generations of military tech later.

The heat is the big problem. Heat sink and--as a tinker, it just popped into my head--something like a short, wide piston to force a puff of air through the chamber when it cycles.

The primer can be integrated--priming compound covered with a binder. Still impact-fired (which I doubt will go away with any projectile rifle, for durability's sake) and would burn off with the propellant.

The big issue as far as Average Joe is concerned, is the utter lack of way to clear a stoppage--no casing means nothing for an extractor to yank on, and possibly no extractor at all. Even if it uses a metallic primer that needs to be extracted, try lodging a round into a sandy chamber and then pulling it back out without just ripping the primer off.

I do expect caseless ammo to catch on in the far future, if just because of a lack of material. And I expect it to hold on until energy weapons, at about the same time of the first fishing expedition to Europa.

Edit: More likely than caseless ammo would be a bullet with a hollow base containing a smaller amount of more potent powder. That would effectively solve both the weight-per-round problem, and the heat dissipation.Stoppages could be cleared by an extractor that must be manually engaged, and could hook into a driving band on the bullet, which in turn could be formed as a cannelure to hold the 'slug' of propellant in place.

Note to self: timestamp this, and check the nearest patent office.

 

[9teenEleven]

The other issue is the you generally need some kind of power source to load each round. IMO batteries in guns are bad juju.

 

[Jim Watson]

Sorry, Deus, almost all of that has been tried.
The distant ancestor of the Winchester, the Hunt-Jennings and Volcanics had hollow base bullets filled with powder. Since black powder is not very energetic, they were not very powerful. The only high energy compound known at the time was mercury fulminate and that would demolish the gun before enough could be used to drive the bullet.

Voere had a bolt action with bullet molded into a caseless propellant charge. There was a groove around the propellant cake and an extractor on the bolt head so you could unload without firing the shot in the chamber. A bolt action sporting rifle, it was not likely to overheat the chamber. It was electrically fired; two 15 v batteries claimed enough for 5000 shots.

 

[Nutgun]

If they do succeed you won't be shooting anything anymore. It will be controlled by the goverment for the government. There will eventually be nothing to reload and then we have no guns. Well we will have guns but nothing to shoot out of them.

Cleaver idea.... I'm sure it will be coming, well not coming to a gun store near you soon.

 

[anhedonic]

I wonder if it would be suitable to use a piezo effect trigger for ignition? No batteries to fail and decent voltage to cross a "spark gap" between the bolt face and the primer area of the cartridge. Caseless might require the development of a conductive propellant to complete the circuit, but I think a piezo system could be designed to satisfy reliability requirements.

Removing the mechanical components from the ignition would open up a lot of flexibility in placement of the trigger group (especially on bullpup designs!) and modularization of the unit could make replacement of the FCG as easy as pushing a retaining pin out/in.

Just thinking out loud while I drink this coffee...

 

[Justin]

In the early 1990s, Remington released an electrically -fired hunting rifle called the Etronix. I have no idea if the concept and product were sound or not, but a Google search will turn up a rant by a print magazine gun writer ranting about how all the jerks on the internet forums were responsible for the demise of the Etronix. It's a fairly hilarious read.

 

[FIVETWOSEVEN]

Post a link, I want to read it!

One thing about caseless ammo is that its not as durable and is more prone to getting wet than cased ammunition. The idea has merit and room to grow but it has these setbacks.

 

[Robert]

http://lmgtfy.com/?q=Demise+of+the+Etronix+Rifle

 

[Slamfire]

HK tried caseless ammo, long ago. It didn't work. 1960's or '70's technology, as I recall.

Actually it did work. I heard that by the late 80's the Germans were just about to adopt case less ammunition, but then the Wall fell down, and the costs for reunification buried the idea.

http://www.65grendel.com/art002arammo.htm

The closest to adoption of all of the exotics was the caseless cartridge, in the form of the Heckler & Koch G11 rifle. It was actually about to be adopted by the German Army to replace the 7.62mm G3 (Germany never having adopted the 5.56mm NATO) when the Cold War ended and the Berlin Wall came down. Military re-equipment spending promptly halted. H&K were financially ruined by the cancellation of the G11 and fell into the hands of Royal Ordnance, where they have earned their keep by sorting out the long-running problems of the British Army's SA-80 rifle, but that’s another story\\\\\\\\u2026

 

[Artiz]

Trying to fix something that isn't broken, especially in the ammunition area, is pretty senseless... and of course, it doesn't work.

 

[Jim Watson]

Etronix electric primers are listed at $200 a thousand, none on hand at Midway.
Brass, bullets and load data are standard; so you could rebarrel an Etronix rifle to about any caliber.

The Kricotronic .22 of the 1980s fired standard ammo by putting many amps across the rim.

 

[TedP]

Metal Storm. Caseless, electronically fired. Ridiculously cool.

http://www.youtube.com/watch?v=d8hlj4EbdsE

 

[-v-]

Caseless ammo gives an instant weight savings on ammunition. A standard load of a .223 is say a 62 gr bullet over 23 or so gr of powder gives you a total projectile + propellant weight of 85gr. A loaded .223 round weighs markedly more than 85gr because of the casing. Cut that out, and you can have much more ammo with a lot less weight.

An equally interesting idea I saw was the use of a polymer case (as in everything but the rim was plastic). This also drastically drastically cut weight, and heat build-up, since the plastic serves as an excellent thermal insulator. I recall they were being sold in '05 or so, but I have not been able to find it since.

As for brass carrying a lot of heat out of the rifle: I doubt it. Brass is a very good thermal conductor, so most of the heat from the powder goes through the brass to the chamber. The ammount of cooling that brass provides is in the neighborhood of negligible and basically none.

 

[Jim Watson]

You ever had an ejected case down your collar? I think there is appreciable heat carried off by the brass.

 

[Shadow 7D]

The army was working on liquid propellant for the latest generation of artillery, but the crusader project was canned, according to what I read, the had everything about the system except the liquid propellant worked out.

 

[-v-]

Jim: Yes, there is considerable heat in that brass, you can't have heat flow without the medium heating up. The point being is brass is a very POOR insulator. Any heat from the burning/burnt powder passes through the brass to the receiver. (Heat can't flow from cold to hot, after all) The brass naturally heats up in this exchange.

Also, having a rather low specific heat (Jouls needed to raise 1gram of material 1 C), it takes relatively little energy to raise the temperature of the brass. Once its temperature is equal to that of the burning gases and/or the receiver walls, its stops absorbing any more energy. Any additional thermal energy flows through it to cooler parts of the firearm (receiver, chamber, etc.) Thus, while a freshly fired shell casing might feel quite hot, it has carried away a fairly small amount of thermal energy from the firearm, with most going into the hot gases, receiver, barrel, and air. Thats why after brass lays around for 10 seconds or so, its room temperature, while the receiver or chamber are still hot for a considerable time afterwards.

About the only time that brass provides any measure of cooling is when a fresh, cool, cartridge is chambered. Upon which, it also begins to heat up until it is at the same temperature as the chamber, or shortly, the same temperature as the burning propellant, which introduces yet more energy into the system.

 

[LaserSpot]

I think practical caseless ammo will be similar to Gyrojet rocket rounds, but with active steering. It will have pinpoint accuracy at any range.

“As a Recon man I liked the weapon just fine: light, quiet, low-maintenance, and a hell of a punch. It was not silent, not like the true silenced .22 Hi-standards we often carried. But it was quiet, made a sort of "Psssssst!" It sounded like air escaping from a truck tire, maybe a half-second long. I fired it in camp several times, demonstrating it, never got any attention at all.”

http://www.deathwind.com/review_2.htm

 

[Bill_Rights]

Those were a lot of good responses!

Amazing. I think we THR folks have about covered it. Every issue has been touched on, maybe twice or three times.

In the RFP (request for proposals), the Army does acknowledge that there has been 50 years of effort put into case-less, propellant-cased and combustible-cased ammo. A lot has been learned.

I think the gist of the present-day drivers are 1) weight has just become an overwhelming concern, what with batteries and electronics a foot soldier might have to carry and 2) materials science and research just progress along and, who knows? - the answer-material might already have been discovered and we just haven't realized it yet.

Apparently, it is fairly common to use some version of case-less or combustible-cased ammo for larger calibers (30 mm and up). I guess that is because the gun itself is part of some vehicle system and the ammo supply can be kept dry and relatively controlled. The real, new challenge is to come up with small arms ammo (5.56 mm, 7.62 mm and 0.50 cal) that is lighter, since those are the man-carried calibers.

A huge issue we only touched on above is water permeation. Small arms ammo has to be usable even after dunking in water. If there is any water permeation, you'll get incomplete detonation, residue in the firing chamber, and build-up from there leading to failure-to-feed or bolt not in battery.

I think one place the Army is expecting breakthroughs is in coatings or films that are simultaneously waterproof but still combustible themselves. The issues of not having brass to expand and seal blow-by (Wikipedia article) and being able to extract a non-fired round will require some changes to the firearms. But I think (I could be wrong) the idea is to get this done sooner rather than later and get it into essentially the current generation of small arms, probably with some changes to bolt face and extractor form and function. Partly it is a matter of cost.

Yeh, I know. It is hard to believe, what with the 100s of billions the military spends every year, that cost is an issue. But the military lives under quite tight budget constraints. It is only the legislators in Washington that live under no budget restraint.

 

[WardenWolf]

Caseless ammo won't be practical for quite some time. The problem, as has been stated, is heat buildup. Given enough heat, the rounds can actually start to cook off, resulting in a mag dump. The heat problem would necessitate a cooling system that would eliminate any weight benefits. There are also significant fouling problems, as friction rubs off unburned propellant behind the projectile. And lastly, there's issues with the rate of burn causing insufficient acceleration.

 

[double bogey]

I think a system should just use projectiles: Load a bullet, inject a combustible mix in a chamber, spark it, repeat process. Develop a method to remove heat. Power weapon electrically like mini guns, use waste pressure to run generator to keep battery up. Maybe workable in a crew served weapon, may be too heavy for one person. I think with our technology this is very doable.

 

[Shadow 7D]

Look up the crusader project, then go look up liquid rockets, they have a nasty habit of going kaboom, and that would be very bad for what ever happens to be around when the whole thing goes, consider the valves have to take the force of the explosion and keep working, repeatedly.

Second, arty uses propellant bags, so it is caseless.