Light gas guns

[Kliegl]

Ok. I told you the stove was hot, but, if you have to touch it to see for yourself, I won't stop you. Peace.

 

[Strykervet]

Sure they are. Its the only source of energy in the system.

True, to a point. But you misunderstand me, I wasn't clear. From Wikipedia:

"The limiting factor on the speed of an airgun, firearm, or light-gas gun is the speed of sound in the working fluid—the air, burning gunpowder, or a light gas. This is essentially because the projectile is accelerated by the pressure difference between its ends, and such a pressure wave cannot propagate any faster than the speed of sound in the medium. The speed of sound in helium is about three times that in air, and in hydrogen 3.8 times that in air."

That is what I was getting at. And I thought hydrogen was six times, but if it is only 3.8 vs. 3 for helium, it would be much safer to use helium. I want a light gas gun, not a combustion light gas gun (although that would be MUCH cooler!). The combustion light gas gun has already been weaponized, the light gas guns I know of are scientific devices. In combustion light gas guns the gas is set off with a spark plug getting even more velocity (and pressure).

I don't want to use a cylinder that tough, or a piston that precise, and I don't want a design that complicated. The whole idea is to keep the single shot simple. So simple it will have a just a disc that will rupture at the right pressure thus allowing the light gas to push the bullet down the barrel blank. The barrel doesn't even need a chamber, just enough material removed to allow a bullet to seat up to the rifling. I'm thinking about a .223 since it would probably be the safest and fastest combination I could do. Certainly couldn't use run of the mill bullets or twist rates.

As a safety to keep the piston/barrel assembly from blowing out, I figured I'd vent the chamber just past the point where the piston compressed the gas enough to blow out the valve. Think porting, several holes drilled in line with the cylinder.

Overall it should be fairly safe, and of course I'd be safe enough to remote fire it. The prototype would probably be hard on parts, particularly the piston, the big problem is how to stop it without it becoming damaged or damaging the barrel assy. But that is how you learn.

Eventually I'll get the equipment I need, the mill and the lathe, and although I don't need it for this one project, my mfg. license (I want to build rifles and AOW's, mostly umbrella and cane rifles). I'll have to shelve the idea for now. I just thought some constructive discussion could come out of here, perhaps some ideas, but I guess not. Typical internet shallowness... Please close this, delete the whole thing, whatever. Not going where I wanted it to go.

 

[Strykervet]

If anyone is interested there is a regular "International Symposium on Ballistics" held in which the best minds in the field come together and present bleeding edge research for their peers.

It is always interesting, often surprising and sometimes a little scary.
http://www.ballistics.org/index.php


...cool stuff like this (see attachment)

Thanks, that is pretty cool. I'm always interested in stuff like that. A ceramic SAW barrel... I don't know if I'd have wanted one when I was a SAW gunner, but who knows? Something lighter certainly would have been nicer, and not having the barrel turn white hot and melt like in a cartoon would be nice too.

 

[Sam Cade]

"The limiting factor on the speed of an airgun, firearm, or light-gas gun is the speed of sound in the working fluid

K, here is the issue, you arent understanding how an LGG scales.
LGGs allow you to get on the happy side of propellant charge to projectile mass ratio


Someone answer this question and explain your answer

Q: If I want to achieve the same level of performance as a .223 rifle using a LGG do I have to use more or less of a given propellent?

Not going where I wanted it to go.

Lots of good information in this thread keep at it....

 

[Sam Cade]

A ceramic SAW barrel... I don't know if I'd have wanted one when I was a SAW gunner, but who knows?

You know everyone would always be trying to sharpen their knives on your weapon.

 

[Maple_City_Woodsman]

No, that's not it.

Well, if you had bothered to read anything in the links I quoted above my text, you should have seen an article about gas pistols, and a picture of a revolver which fires exactly the type of shells i was talking about...

Now, about your crazy NASA gun:

I am aware of antique European air rifles which used an ether tank attached to chamber to boost velocity via 'dieseling'. They had a mechanical trigger linkage which would quickly open and close a valve, thus injecting a measured amount of gas just before the piston fired. How well this actually worked, I don't know. It also sounds hella dangerous.

Additionally, you may also find the repeating mechanism you seek in the world of air guns as well. Conventional repeating airguns use a hollow bolt probe to transfer the compressed gas across the loading tray into the chamber to a fixed barrel. It seems like you could use this to solve both your problems of bore reduction as well as the issue with feeding additional rounds - if you made the barrel movable, then a blow-forward type mechanism would allow the barrel to move away from a fixed bolt probe,and strip off an additional projectile as it returned to place. This would also allow you to make use of the way a conventional bolt probe seals against the chamber walls.

If through some miracle you were able to combine the two designs, then you would have man portable gun similar to what you seek.

 

[Mr.454]

Well one of the issues is to figure out what kind of projectile you want to fire down the barrel. Probably some light weight tungsten alloy I would think, from a sabot of course to keep the barrel in one piece. So for the sake of this discussion I would focus on a long distance anti-tank weapon or a small caliber anti-material weapon. It could be used as a weapon, it uses gun powder to multiply force but would have size limitations much like a hydraulic system. If you had a large enough hydraulic piston system you could lift the world. So I would try to look up the figures on the relationship between piston size, chamber length, and projectile speeds.

 

[brickeyee]

Maybe not for a combat rifle, but for a long range thing, it might be feasible

.

Guided projectiles (as in steering) are always going to be more accurate than a ballistic (unguided) solution.

the US has not had an actual ICBM (Inter Continental Ballistic Missile) in a long time.

The war-head bus for MIRV is guided in flight above the atmosphere to release the re-entry vehicles (warheads).

Some of them are even guided in the atmosphere to improve accuracy.