Hydraulic case forming

[Newton]

Greetings
I am sure most people know about hydraulic case forming using a special die and water to form cartridge cases
Rather than the normal fire-forming which uses expensive components.
The hydraulic method can however potentially be a bit messy

I wonder if anyone has looked at using a - Pneumatic process to do the same work ?
Would be a lot cleaner and not messy
Should not be too difficult to make the necessary parts ?
I do wonder what kind of air pressure you would need though ?
300 Bar is not unusual in some engineering processes

[oafpatroll]

I would want no part of pneumatic equipment operating at those sorts of pressures. There be whole flights of dragons in my chickenhearted opinion.

[janfred]

You need more than 20,000 psi for that. No, thank you.

Due to the uncompressable state of liquids, if something should rupture the pressure drops to zero pretty quickly without sending shrapnell everywhere. On the orther side, gas would heat up considerably under the pressure required and it tends to be very unhealthy being in close proximity to the event.

[Newton]

OK
You do realize that you are very close to something very similar ..
Every time you fire your rifle.

So make your die setup a very short clone of something similar to your rifle action and barrel
A die is in essence a rifles chamber
All one would need is one single valve operated "pop" of air - could even do it from a distance.
We are using compressed air which is a renewable resource rather than components which are consumables

Engineers work out these sorts of calculations all the time
Heavy equipment hydraulics work at these pressures all the time.

I will chat to my machine shop engineering buddy tomorrow

[Treeman]

I can not see this being a problem or very dangerous if done properly. I do however see a tremendous amount of money being spent in making mounting and realizing the objective. This will not be a desktop item, more like a half ton workshop tool.

[JamesNotBond]

Would it be possible to change the form accurately in a cold form such as suggested?

[oafpatroll]

OK
You do realize that you are very close to something very similar ..
Every time you fire your rifle.

So make your die setup a very short clone of something similar to your rifle action and barrel
A die is in essence a rifles chamber
All one would need is one single valve operated "pop" of air - could even do it from a distance.
We are using compressed air which is a renewable resource rather than components which are consumables

Engineers work out these sorts of calculations all the time
Heavy equipment hydraulics work at these pressures all the time.

I will chat to my machine shop engineering buddy tomorrow

There's likely much more difference between a rifle being used to fireform a case and a valve operated pneumatic system doing it with air than you suggest. Time being the one that leaps out at me. The entire operation is nano-seconds long in the rifle and I very much doubt that could be true in a pneumatic device and therefore the obturation that causes sealing to occur in a rifle chamber is not guaranteed to work the same. It may not work at all at practically achievable pressures and may require a different method of sealing. 

I don't get your point about air being 'renewable'. Air just is. Unless you were generating the considerable amount of energy required for a contraption like this to operate from the sun or similar there'd be nothing more or less renewable about it.

Failures in hydraulic and pneumatic systems are barely comparable in their potential for destruction. There's a reason that compressor tanks are often tested with water pressure and it's not because its easier than doing it with air.

Google for some info on catastrophic failures of pneumatic system components for some eye opening viewing. The first such thing I experienced was a compressor that failed behind a nearby mechanics workshop. People reported hearing the bang from well over a kilometre away and two exterior walls of the structure were flattened. One of the guys in the shop was killed and the other was as good as deaf afterwards. 

[janfred]

...

I will chat to my machine shop engineering buddy tomorrow

What did your machine shop engineering buddy say?

[jager]

The stored potential energy in a pneumatic system is in a very very different league to a hydraulic system operating at the same pressure.

If a scuba tank fails hydro testing it does so with without much fuss, but if it fails while full of air, it takes a wall or a car or 2 with it.

[Treeman]

I said previously I do not see this being a problem, I think I need to retract that statement. Last night while I waited for the night to pass I built this machine (I do these things in theory then approach the experts to find where I got the theory wrong), I started with a die set and ended up using a chamber and barrel basically - simple. Then things like keeping the pressure in the case and not just everywhere meant sealing the case mouth when it was in parent form and then keeping it sealed while it formed and moved, changed shape without the pressure going around sides of case and making a mess.
I went back to a die set and then made a die that would handle the pressure without blowing the case out bottom of die, I still have not found a way of sealing the neck of case to contain pressure while case forms.
I am now on back of mind all the time nearly 24 hrs, still have not built a system that will work even in dream world.

[janfred]

Now you just need 30,000 psi to put in there...

All jokes aside. You basically you need to force in excess of 8 lt of air into a 4ml case.

Is it possible? Yes. But those of us with any sense know enough to want to be far away from the experiment.

[Treeman]

Now you just need 30,000 psi to put in there...

All jokes aside. You basically you need to force in excess of 8 lt of air into a 4ml case.

Is it possible? Yes. But those of us with any sense know enough to want to be far away from the experiment.

*******************************
I was in a building once watching a bloke through some hanging like plastic sheets doing something around or on a hydraulic kind of thingee from a oil rig (I was working for BABCOCK at time) this guy suddenly like jerked and grabbed his chest and staggered off, I thought he had had a heart attack from where I was. I was later told that the thing they were testing had sprung a leak and it had basically shot him in the chest ? I answered that I had not seen any leak.
This was 40 years ago and I knew nothing of the subject at time and have always remembered that the guy I spoke to said the leak could have been like a hair thick and at "that "pressure" would just go through steel, brick whatever.The guy died because he had oil injected into his lung, or so I was told.
I know this pressure cutting to be true because at a later job we used a Hammelman V12 engine to run a high pressure water cutter to cut holes in buildings where dust was an issue. I also have a scar where I shot a hole in my finger when I met my first high pressure cleaning tool - Yip! I put my finger in front of it to see how strong it was  quiet strong I very quickly found,  still have the lightning bolt knuckle to knuckle scar.
So yea it could be a scary experiment.
I have not yet found a way of sealing the case as it changes form and caliber.

[Tripodmvr]

Newton, when you shoot store bought ammo in your rifle, you mostly get good accuracy whilst at the same time you are fire-forming the brass cases. I developed loads in new cases and got excellent results. A small adjustment might be necessary on the use of the cases for the second firing. I therefore don't see any need for a special procedure to fire-form cases. My old 243 ammo shot wonderful groups after the rifle had been Ackley Improved.

My advice is thus to use normal reloading principles and shoot new cases in the discipline for which you need them.

If you are converting cases to a different calibre then such a procedure might be necessary.

[Treeman]

Yea, I thought he was talking wildcatting stuff ? not just minor case forming.

[Newton]

...

I will chat to my machine shop engineering buddy tomorrow

What did your machine shop engineering buddy say?

He thought that it might be possible - with a lot of problems that would have to be solved
The pressure spoken about here did not seem to scare him
I have not yet found out how much pressure you need to move cartridge case brass ( apart from the web and head ) a few thou mm ?
It might be in the realm of quite reasonable ?
The pressures generated by a normal discharge are what happens when the propellant ignites
To "form" the brass might not require anywhere near these sorts of pressures ? 
A good engineer always designs a - well thought out pressure release / relief valve