Firearms using liquid or gas propellant?


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31 December 2008
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Does anyone know of any experimental firearms projects or prototypes (not artillery, something man-portable) designed to use liquid or compressed gas propellant instead of gunpowder? The magazine could hold a tank of fuel and a bunch of bullets, no cartridge casings required, nothing to eject except in case of a misfire, variable amounts of propellant possible. It seems like a good idea in concept but I have never heard of it being tried except in artillery. Thanks!
I presume you mean other than one like the Girandoni air rifle used by Austrian snipers against Napoleon
Correct, I meant a combustible propellant rather than compressed air, though if you know any modern combat air guns I'd certainly like to learn more.
Some work was done to incorporate regenerative liquid propellant gun technology into the now defunct Crusader program. None have come into service AFAIK. You might like to take a look at this book here,

As for small arms, I know of no active R & D efforts. Perhaps it would be impractical logging liquid propellants around an active combat environment but I would be interested to now of any R & D efforts.
I heard of project used liquid propellant instead of powder in a Rifle case. Only anectodetly.
Both the US Army and the US Navy pursued liquid propellant gun research in the 1990s (GE and Martin were primes early on). While interesting, the projects eventually came up against the same problems as liquid-fuel missiles -- the need to provide fuel as part of the logistical train, plus the safety auspices of energetic fuels being stored on a ship or in a tank. Also, it seemed to be the answer to a question no one was asking.

Here's a reference to non-US research using a 40mm round propelled by methanol and nitromethane (Sunday! Sunday!!):
One of the difficulties is that oxidizer/fuel mixtures and monopropellants tend to simply detonate when ignited, where gunpowder deflagrates. To do a liquid propellant right, you generally need to have something more akin to a liquid fuel rocket injector system... far more complex.

But then, there's always the spud gun, of which there are a very great many. I've seen 'em down to pistol size. But more typically they're of recoilless rifle size.
Yes, and nitromethane is an interesting case. It's quite difficult to ignite, in fact, dragsters use the equivalent of twin 44-amp arc welders to fire it off.
There are also electrothermal guns, though they have their own difficulties.
Maybe a little off-topic, but here it is anyway: My personal assessment, based on 20 years of personal interest in firearms, and 12 years of working with weapons and ammunition, is that we might see new cartridge cases made of novel materials, or new (solid) energetic substances that allow more efficient cartridges, or more aerodynamically efficient projectiles.

But with regards to a valid alternative for the self-contained-cartridge firing small arm, I don't think we'll see that until the energy and power supply problems of hand-held directed-energy or electromagnetic weapons have been solved. I'm sure this will happen eventually, but I'm not holding my breath ;)

Regards & all,

Thomas L. Nielsen
At one time a 25mm gun with "caseless" ammunition was proposed for the F-15 (F-X). "Caseless" in this context means the case is actually constructed of propellant and is expended during the firing event. I know we sunk a bunch of money into it but it never went into production, so I'm not sure if it was a cost or performance problem.
Fascinating !!

FWIW... Spud gun fuel variants:
I vaguely remember a book where a prototype UK tank with liquid ammunition propellant (sic) was hidden for safety at outbreak of military coup during field trials in Middle East. 'Liquid propellant' allowed a low, humpy turret like a tank-killer plus surprising capacity for ammunition storage. The 'extraction' team wired the crucial fuel-injector breech with C4 and were about to blow it when helo's gearbox graunched. Within a few chapters, they had Saudis, coup leader & IDF chasing them...

Couple of reality checks: They had designer along to keep the one-off prototype sweet. Yes, it had a bunch of issues.

IIRC, book title was something like '{1 forgotten word} target', being a UK version of 'target of opportunity', where-in every-one who could safely range must attack. And, yeah, they're 'it'.

IIRC, book began with a seige take-down, and was sequel to one where protagonist's wife is killed by bomb on plane meant for him. There's a young son...

Sorry, I've just spent half-an-hour googling titles / subject / author without success...
Firefly 2 said:
rickshaw said:
Would the Gyrojet weapons qualify for what you're looking for?

Didn't those little rockets use solid propellant?

They did indeed.

See e.g.,2083.0/highlight,gyrojet.html

Regards & all,

Thomas L. Nielsen
Firefly 2 said:
rickshaw said:
Would the Gyrojet weapons qualify for what you're looking for?

Didn't those little rockets use solid propellant?

Yes, but it would not be a stretch to suggest they used a gas propellant. ;)
Another weapon you might like to consider is the Zalinski Dynamite Gun - a pneumatic weapon which could fire a large, half-ton charge of dynamite to over four miles. Adopted briefly by the US Army and Navy, they lasted only about 6 years in service at the turn of the 20th century.
Although not an Army but an Air Force Project - in one of Anthony William's books he mentions a proposed liquid propellant gun armament for interceptors. This project of the early 1950s was to be of the Gatling gun configuration and had a caliber of 51 mm with a high rate of fire (3000 rpm). Does anyone have more information about it?

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