View Full Version : Interesting idea

December 28, 2010, 09:17 AM
An avid shooter, reloader and hunter; I have been pondering something about ammunition for the past couple of days: Is it possible to make a cartridge that propels a projectile using liquid? I know physics to an extent, but I am no expert on it.

So, I think it will work like this: You fill a case with some sort of liquid, and add a type of primer in it that won't be affected by liquid. When the firing pin strikes the primer, the explosive force pressurizes the water forward and launches the projectile. Kind of like a combustion engine, with the exception of using an inert liquid and a high explosive primer.

I guess one of the questions would be: "what happens to the liquid?". Well I would assume it would just vaporize-depending on what type of liquid you use. I think this could be neat for the military and heavy machine guns-the bore would stay much cooler due to no hot gasses.

Of course, I am not trying to reinvent the wheel; I just like the science behind firearms and am just wondering if this has ever been tried before, or if it's even possible.


Mods, if this thread needs to be moved, go ahead.

December 28, 2010, 11:10 AM
What you are discribing is hydrostatics. Would it work?....maybe, depending on many factors. Would it be efficient?....no. Liquids do not compress so you would need your charge to be sufficient enough to force the bullet out of the barrel at the speed which you desired.

Art Eatman
December 28, 2010, 11:19 AM
You still need something to create the force to "hammer" the water. All you're doing is creating some ungainly sort of creature. It's a "Why bother?" sort of deal, seems to me...

Plus, your primer and accelerant would then have to accelerate the mass of the water as well as the projectile, not to mention the accelerant itself.

(Remember that when you calculate recoil in a conventional firearm, you must add the weight of the powder charge to the weight of the bullet.)

Brian Pfleuger
December 28, 2010, 11:22 AM
The only energy you'd get would be from the primer. You can't get energy from nothing..... If the liquid is not being altered by the primer but simply moved then you are entirely limited by the energy contained in the primer ignition.

You could do something with hydraulics, surface area differences and whatnot. You'd be doing it the opposite way of a jack or car lift. So you could get "speed" rather than "force".

All in all, I doubt it would be useful in any way. Interesting, but useless.

December 28, 2010, 11:26 AM
All true. The amount of force required to compress the liquid to the pressures needed, would virtually eliminate the need for the liquid.

Now if you could invent "cold fission" from a liquid...hmm

December 28, 2010, 11:47 AM
The way I look at it is water can't be compressed, so it would deem more efficient if you could get it to move somehow. Hydrostatic compression is what I am thinking about. If they can do it on the engine of a car, why can't it be done with a rifle? Yeah we're talking combustion vs hydrostatics, but it's still the same principle of liquid creating energy by outside forces.

Let's take away the "usual" and think about this realisticly: Take away the factors of added weight, recoil, etc, etc. Build the cartridge, then work your way up to reducing recoil, case size, efficiency, etc.

Firearms would definitely have to be redesigned, but hey, I think it's a cool idea.

December 28, 2010, 12:05 PM
The part missing,as you reference engines,is the liquid fuel is atomized,mixed with a large qty of air/oxygen,then compressed .I suppose ,in theory,that an oxygen/propane or? could be pressurized into a large case,and something might go "pop" but smokeless powder works better.
I think old Don Garlits swamp rats would have gone faster is he fuel injected Blue Dot.Head gaskets would have to be tough.
To piggy back on your idea,though,maybe some form of microspheres filled with water...water injection? Add a little steam pressure?
Then the old Montessa 250 LaCross MX bike I had liked castor bean oil for 2 stroke oil,it ran stronger......

December 28, 2010, 12:21 PM
That's what I am thinking-steam pressure. Though cold pressure would be desired more so.

The logic behind this idea: Not to neccessarily reinvent the wheel; rather make a cold bore machine gun of some sort. Rather than super heated, super efficient gasses, how about super cool, and "efficient" liquids.
There may be other benefits to a design like this (sound suppression etc).
I mean, if they can use water jets to cut several inches of steel, surely you can manipulate a few drops of water to move a bullet.
Also, it's not like we would be using a 30-06 case full of liquid to make this happen. All the designs would have to be changed to fit the cartridge.

December 28, 2010, 01:28 PM
It was said pretty well, liquid doesn't compress, something has to move it. Once you come up with what moves the liquid you don't need it any more. Now if you could have a little super heating element that could bring the exact right amount of water to superheated steam pressures in a flash that might work.

The only liquids are multiple liquid chemical reactions such as liquid rocket fuel.

Gunpowder is pretty darn efficient for moving a projectile.

December 28, 2010, 02:35 PM
The military uses a water charge to mitigate the backblast of new versions of the SMAW so it can be fired from cover. Think of a plastic tupperware container that does nothing but disperse the energy of the backblast into the water it contains.

The problem with using a liquid as a propellant is energy density. Gunpowder is an "all in one" package of fuel and oxidizer. I guess nitroglycerin (a liquid) would fit the bill for a liquid propellent, but there are some stability issues....

Also there are pressure issues, gunpowder burns instead of exploding. Most liquids are either inert or exploding. Inert doesn't give you any advantage, because for the liquid to expand into a gas takes energy that should be pushing the projectile.

If liquid was added to the charge as a way to mitigate excess heat for rapid fire weapons, that might be interesting.


December 28, 2010, 02:52 PM
Ya the primer would have to fit inside the cartridge and slide.The firing pin would have to hit with such speed and power as to transfer the energy to the water in the case,thus pushing primer forward and inturn pushing water forward and then pushing projectile forward. There is potential there guy.:)

December 28, 2010, 03:00 PM
If liquid was added to the charge as a way to mitigate excess heat for rapid fire weapons, that might be interesting.

This too. I am not even thinking in regarding of a complete liquid usage here.
Since this was mentioned, I have to ask, could you use a hybrid compound?
Where you have some sort of liquid seperated from the propellant, and it's purpose would be to cool the barrel, and increase pressure and velocity (liquid causing pressure increase), while using extraordinarily less propellant? Since liquid takes up more space than powder, you would increase pressure from the tighter space right?

We all know that water in a barrel isn't a good idea; but with that idea, could use reverse engineer to make a liquid helpful in a cartridge's performance?

We all have seen what happens when you try to screw a nozzle on a hose, while the hose has 40lbs of pressure running through it; doesn't work out so great. So with that concept, and the idea to somehow creat that pressure, could you make a liquid projectile?

Hydraulic ram pressurizes liquid into motion = liquid into motion = projectile exiting barrel in front of liquid = flying projectile and cool barrel.

This probably sounds like nonsense.

December 28, 2010, 03:24 PM
There are explosives in liquid form, such as nitroglycerin. Nitro is a bit volatile so they mixed it with cellulose.

Most explosives, liquid or solid develop a lot of pressure. More pressure than gun powder, most likely.

Leakage would be a problem. If the explosive were jelled then you'd reduce that a bit.

But one problem with "plastic" explosives is that they tend to break down over time. Often when they break down they become volatile.

December 28, 2010, 07:41 PM
Years ago, there was a tv series on either PBS or Discovery with a colorful character who made all kinds of goofy and entertaining stuff.
He made a cannon, using gasoline and a spark plug.
It worked pretty good, too.

December 28, 2010, 10:10 PM
Maybe you could use "Hoppes#9" as the liquid, then you wouldn't have to clean the gun when you finished shooting, Just a thought.

December 29, 2010, 11:50 AM
Tater gun :D

December 29, 2010, 02:23 PM
Maybe you could use "Hoppes#9" as the liquid, then you wouldn't have to clean the gun when you finished shooting, Just a thought.

I like that idea. How about we also add a brush around the bullet so we never have to clean the barrel?