$ ammo = resurrect caseless ammo?

[PAshooter]

Internal combustion engines seem to avoid detonation ("knocking") by careful design and fuel selection

Different animal.

 

[novaDAK]

After reading this thread, I'm getting the urge (again) to purchase a stainless Ruger Old Army revolver.

better decide quick...I heard over at RugerForum.com that the Old Army isn't in the 2008 catalog

 

[PAshooter]

better decide quick...I heard over at RugerForum.com that the Old Army isn't in the 2008 catalog

True... check their web page... all the BP revolvers are listed as "discontinued."

 

[230RN]

Percy Shelley:

What if the firing chamber were filled with a combustable gas? The bullet could seal the front and a metered amount of propellent is introduced into the chamber. The propellent would be fired by a spark like a gas engine. A new bullet fed in to seal the barrel and another metered charge shot in.

You really can't get the energy density required for high performance. A gallon of gasoline weighs about 6 pounds, and you have to mix it with six times fourteen pounds of air ( = 84lb) to get the right mixture ratio (every carburator mech knows that). That means about 1120 cubic feet of air. ( A cubic foot of air weighs about 0.075 lb.)

Even if you mixed a gallon of gasoline (vaporized) with pure oxygen, you'd still need about 17 pounds of oxygen gas. Scale that down to catridge-ish sizes measured in cubic inches, and you can see that it's pretty impractical.

However, for spud guns, the energy density of a fuel-air mixture is enough to throw a spud and make a bang and make everybody go wow.

Bear in mind that FAE bombs mix a large quantity of fuel with an enormous amount of air before they ignite the mixture, although some FAE fuels contain oxidizers either in the fuel as a mixture or oxygen and other oxidizers chemically combined with the fuel.

http://www.fas.org/man/dod-101/sys/dumb/fae.htm

In the animation in the above link, you will see the fuel being blown out of the missile and dispersing. If you look carefully, you will see a detonator (a little dark dot) following along behind the missile, which allows time for the fuel cloud to mix with the air before igniting it.

 

[alan]

If you think caseless ammunition would be CHEAPER, a position I personally question, would it function is existing firearms, without likely expensive modifications?

I do not know for certain, but I have my doubts.

 

[brassdog]

Interesting debate...

I remembered the old Trounds from the Dardick being made of celenese (sp) which was a polymer nylon, I think. If I'm wrong let me know.

The trick is to remove the need for extraction/ejection.
I could see a redesign for the AR/AK variants with a tighter sealing bolt and redesigning the cartridge with a longer bullet that has a hollow base with the primer compound inserted first then the "casing" being made out of the powder itself. The idea being that the primer igniter is integral to the cartridge like the old pin fire cartridges of the 19th century. So that the firing pin strikes the igniter assembly which then transverses forward to strike the primer. The bullet with the igniter would then be propeled down the barrel.
That's just the first thought. Although a completely new system would probably be easier to design than a retrofit.

 

[ThomasT]

Thanks to everyone with the feedback on a daydream gun and propellent system. I haven't heard of the other experiments you guys mentioned.

I guess i have a lot of faith in shooters and gun companies. It seems like every time the anti gun crowd gets something banned like lead shot the shooting community just finds another way around it.

Ammo prices are high now. When the war winds down as all wars eventually do there will most likely be a glut of the ammo you guys like to shoot in your 223s.

I'm just shooting my 22s and saving my high dollar stuff. To me shooting is shooting.

 

[230RN]

Ratshooter:

I'm just shooting my 22s and saving my high dollar stuff. To me shooting is shooting.

You're smarter than me. I'm a wastrel.

Alan:

If you think caseless ammunition would be CHEAPER, a position I personally question, would it function is existing firearms, without likely expensive modifications?

Well, that would be one of the design goals. Not all design goals are actually met. The point of this discussion (in my opinion) is to stimulate new and "wierd" ways of accomplishing a really viable caseless ammunition. This kind of brainstorming is a well-known technique for developing creative new ideas to pursue. In "brainstorming," no idea is worthless... for the simple reason that it may generate more ideas.

One of which may actually be viable.

How about this, for a sample brainstorming "divergence" ... we are sort of "stuck" on the notion that a primer "must be" an integral unit all by itself. Can we distribute it within the propellant itself? Could it be ignited from an external source, such as a magnetic pulse or radio frequency wave? Or maybe electrostatically?

Can it maybe be fired from the front end instead of the rear end of the cartridge? Can an igniting method be applied through the projectile itself?

 

[alan]

230RN:

Having myself worked in engineering and construction, I'm not opoposed to "brainstorming". I have serious reservations as to the "workability/practicability" of caseless ammunition.

 

[saspic]

I am not mechanically inclined, but I have questions:

1. What would an electric ignition system mean for the trigger pull? I can't imagine it would require a very heavy pull to work. Would all guns be able to have perfect light triggers, say 2-3 pounds of force for most applications?
2. If the system was truly caseless, it wouldn't need an extraction/ejection system during normal firing, right? Would this simplify the action, or increase accuracy? Of course there would still have to be a system for unloading live ammo and clearing jams, but perhaps it could be optional.
3. Not to drift in a completely different direction, but how feasible are laser pistols? It occurs to me if you had a laser sighter down the bore, it would indicate exactly where your actual, weapon grade, laser would go.

Just trying to see the other advantages to a caseless ammunition system.

 

[PercyShelley]

You really can't get the energy density required for high performance. A gallon of gasoline weighs about 6 pounds, and you have to mix it with six times fourteen pounds of air ( = 84lb) to get the right mixture ratio (every carburator mech knows that). That means about 1120 cubic feet of air. ( A cubic foot of air weighs about 0.075 lb.)

Even if you mixed a gallon of gasoline (vaporized) with pure oxygen, you'd still need about 17 pounds of oxygen gas. Scale that down to catridge-ish sizes measured in cubic inches, and you can see that it's pretty impractical.

However, for spud guns, the energy density of a fuel-air mixture is enough to throw a spud and make a bang and make everybody go wow.

Bear in mind that FAE bombs mix a large quantity of fuel with an enormous amount of air before they ignite the mixture, although some FAE fuels contain oxidizers either in the fuel as a mixture or oxygen and other oxidizers chemically combined with the fuel.

http://www.fas.org/man/dod-101/sys/dumb/fae.htm

In the animation in the above link, you will see the fuel being blown out of the missile and dispersing. If you look carefully, you will see a detonator (a little dark dot) following along behind the missile, which allows time for the fuel cloud to mix with the air before igniting it.

An FAE isn't really analogous to a fuel-air gun; a fuel air bomb is intended to result in a detonation; the flame front propagates via compression. Guns and car engines work on deflagrations, wherein the flame front is propagated by heat and is thus slower.

I am now informed that engine knocking is not an instance of detonation proper; but the idea is the same; get a smooth pressure curve to accelerate the projectile, or piston, down the barrel, or cylinder.

It's also worth noting that internal combustion engines and gun barrels are both 20-30% efficient, which is why I don't think that energy density is an issue at all.

All my numbers for this are from here, by the way.

Gunpowder packs 3.9 megajoules per kilogram, while gasoline packs 34 mJ/kg. Obviously, that's ignoring the mass of the oxidizer, but air's pretty common and cheap, so we can just get it from there. Works for cars, right?

A fifty grain charge of gunpowder will contain in the neighborhood of 13 kilojoules of energy, of which about 4.5 kJ will eventually be converted to the kinetic energy of the bullet. To match that we'll need .38 grams of gasoline and 5.3 grams of air or thereabouts to get a slightly-more-than-stoichiometric mix for optimal ignition. That comes to less than six grams of something that's basically going to have the same density as air.

I get that that comes to 4,100 CCs. I get that 5.56x45 NATO has a case capacity of about 30 CCs. As you say, when you scale it down that much, it looks weak, but since we're switching propellants, why limit ourselves to traditional chamber geometry?

A spherical chamber, for example, would only be 20 cm across or so at that volume. Not something to tuck away easily, but hardly an enormous protrusion compared to, say, a traditional magazine. An oblong chamber could conceivably fit well within a reasonable, dare I say svelte form factor.

 

[PercyShelley]

1. What would an electric ignition system mean for the trigger pull? I can't imagine it would require a very heavy pull to work. Would all guns be able to have perfect light triggers, say 2-3 pounds of force for most applications?

Unless the trigger is piezoelectric (basically the same as those flint-less lighters), the trigger pull could be arbitrarily light, exactly as you say.

2. If the system was truly caseless, it wouldn't need an extraction/ejection system during normal firing, right? Would this simplify the action, or increase accuracy? Of course there would still have to be a system for unloading live ammo and clearing jams, but perhaps it could be optional.

For safety reasons, yes, it would be best to have some means to unload the gun. H&K's experimental caseless G11 did have some provision for unloading a live round or dud from the chamber, but I would describe the design as anything but simple, although most of this came from the need to seal the chamber and from the three round burst mechanism, both requirements that wouldn't have to press so hard in a civilian weapon.

I couldn't speak to accuracy, although Voere seems to think that their 6mm caseless rifle is pretty darned accurate.

3. Not to drift in a completely different direction, but how feasible are laser pistols? It occurs to me if you had a laser sighter down the bore, it would indicate exactly where your actual, weapon grade, laser would go.

If you had a laser, one, you wouldn't need a bore, and two, if we had power sources good enough to make personal laser weapons feasible, nay, portable, then we would be living in a crime free, gleeful utopia where everyone gets a pink pony and free chocolate.

I exaggerate slightly, but the basic problem is that you can't cram enough energy into a batter, at present, to make a useful direct energy weapon.

Which is not to say that there aren't man-portable, militarily useful lasers, of course. Smart bombs need someone to show them which window to fly through, after all.

 

[Gifted]

Problem with a commercial laser is the predominant use of guns is hunting. A laser would have to burn through to a vital area to make the kill. Good luck getting a clean hole. Enough power to burn that deep in enough time to get all of the energy on the same spot is probably going to flash vaporize flesh, resulting in the large ugly black holes generally made by sci-fi weapons. A lot of meat wasted. This is discounting the energy requirements, which pretty much mean you need a HUMVEE to supply the power you need. At that point, a rail gun would probably work better. There you can use hollow points, and tune down the velocity for better ballistics. And you don't need the HUMVEE for just one or two shots, a large heavy backpack would work well enough.

A Piezoelectric ignition would at the worst, be no worse than current triggers. I'm not sure how hard you'd have to smack the crystal, versus a primer, but it would be feasible to just make a drop in bolt. You could even make it so that the pin moves too, allowing you to fire both kinds of ammo. The AR family is already set up, so all you really need is new barrel, new bolt, and maybe new mags(telescoped ammo might need something different). Not much different than current caliber conversions. One of the advantages to telescoped is that caseless will probably use the same shape, which means that the first generation of such can use the same gun without any modifications.

 

[PercyShelley]

I've seen it argued that thermal expansion of water in flesh from a pulse laser hit would cause rapid expansion and tearing, so that most of the damage would be mechanical, and not from vaporization.

Having never fired a weapons-grade laser at a ballistic gelatin target, nor being aware of such a test ever having been conducted, I can't vouch either way. Anyway, until our heat dissipation (CO2 lasers are <20% efficient) and energy storage technologies get better by, oh, an order of magnitude or so, it's all rather academic as far as small arms go.

As for piezoelectric ignition, the best approach may be to use the gun's bolt to smack the crystal, and have the resultant charge stored in a capacitor. The capacitor is only unloaded into the electrically primed round when the trigger is pulled.

In this approach, you have arbitrarily light trigger pull, zero lock time, no batteries, and use electrically primed ammunition, which has been proven since the 40's.

 

[RyanM]

Here's a response I wrote against the laser thing awhile ago, but never got around to following up on:

First of all is the inherent inefficiency of having energy change forms so many times. Electric to light to heat to kinetic. Imagine a laser-powered slugthrower which uses body temperature water (probably with a dye in it to better absorb light) as propellant. The laser zaps the water and causes a steam explosion, which sends the bullet on its way. Not very efficient. I don't have the background to try and calculate what kind of efficiency you'd get from that, but I imagine a railgun or coilgun of the same tech level would outperform it by a good margin.

Then there's the amount of damage it'd do. I have a sneaking suspicion that 4 cm wound width is way off. Unless I miss my guess, I believe Dr. Schilling attempted to use Dr. Carrol Peters' equations to calculate the effectiveness, especially given the statement that this is on par with a pistol. This is a common misinterpretation of Dr. Peters' equations. They tell you the amount of tissue damaged, not the amount of tissue destroyed. The math gives me a headache, and I can't locate my copies of Dr. Peters' papers, but IIRC, a 9mm FMJ bullet damages tissue in about a 2 cm radius. This means absolutely any form of damage, down to very minor bruising.

Duncan MacPhereson's equations, on the other hand, do give the amount of tissue destruction; i.e., the size of the hole (but they are only useful for actual, physical bullets). For a 9mm FMJ bullet, the actual hole would be about 7.5 mm diameter on average (wound cross-sectional area is 57% of bullet area for most roundnose FMJs). Nearly all of this wound area is created by direct contact with the bullet, not by the temporary cavity (equivalent to, though less energetic than, a steam explosion). Direct crush is considerably more efficient at turning kinetic energy into tissue damage, than anything else. Thus, I'm guessing that a 1mm laser would most likely make a hole about 2-3 mm at most.

Now, antimaterial use is a whole different story. But water's heat capacity and heat of fusion make antipersonnel applications impractical at best. Against armored personnel? Basically, the same concept as the FN 5.7mm. Punches through armor better than larger caliber pistols, at the expense of making a much smaller hole. There may be some merit to having a sidearm that can punch through hard body armor (lightweight, reasonably hard slugs at an appropriate velocity will make short work of soft armor), but the reduced wounding effectiveness should be taken into account. I see lasers as special-issue weapons, issued only when robots or heavily armored personnel are anticipated.

 

[230RN]

Thank you, RyanM, great presentation. I think you meant heat of vaporization, though.

And Percy Shelly, thanks for your analysis of energy density of gaseous fuels and batteries. Maybe a supercapacitor? But I think their internal impedance is too great for a really powerful discharge rate --I'm not sure.

...OK, well, anyhow, that's it for this morning. Lunch is in the Tundra Room right down the hall. We'll meet back here at about one-thirty. I hope we got all your lunch orders right.

Oh, wait, I almost forgot. I just got a note from the hotel management, they fixed their Wi-Fi system, it's is up again, so you can all use your laptops in the building.

Thanks. See you all at 1:30.

 

[Zedicus]

I exaggerate slightly, but the basic problem is that you can't cram enough energy into a batter, at present, to make a useful direct energy weapon.

Theoretically their are ways around this, but that would be going WIDELY off topic.

As for the best solution to lower ammo costs, I would go more with the plastic cases that are slowly creeping onto the scene.

Caseless is just to much of a unexplored region at this point.