SpudFiles

warhead052 wrote:Wait, so if you pull back on it, how are you going to make a gun that will actually use them? Some sort of pneumatic piston that pushes them forward or something?

A spring loaded hammer, something like this:

just throwing a reply in here to say its looking great jsr and to make sure I get email notifications haha

Very keen to see thus finshed, its looking good.

Just a niggling thought, converting a 7.62/308 cartridge to pneumatic using a 7mm OD tube insert:

you last videos look like a much more complex version of what i did over a year ago.

Take a female quick disconnect, and remove all the internals except for the rubber washer, and the bearings.... it will hold a 7/16'' steel ball air tight.

I have taken that design up to 350 psi... the only problem i had, was pulling the sleeve back at higher pressure. Your idea of using a hammer to move the sleeve is excellent. I now want to revisit my design.

Thanks!

Did you got some inspiration from here ?

LeMaudit wrote:Did you got some inspiration from here ?

Totally

Doing some prototyping in the meantime, another pop at the hybrid cartridge and a decent fill rig.

Something which came out of this visit, I got to look at a Korean air cartridge rifle from the 1950s. They work on the same principle as the Saxby Palmer air carts, basically a hammer valve where the hammer smacks the bottom of the cartridge pushing it against the valve.

This is the English variation:





This is the one I saw yesterday, bigger internal volume and apparently in the 50 ft/lbs range...

I really like the idea of a large hammer valve that also acts as the check valve for filling, however I've never seen any of us use a fill valve that wasn't a quick connect or a Schrader

iknowmy3tables wrote:I really like the idea of a large hammer valve that also acts as the check valve for filling, however I've never seen any of us use a fill valve that wasn't a quick connect or a Schrader

Looks like you missed this

Revisiting this idea in my head, looks to me that a variation of the Saxby Palmer with a balanced spool would make a lot of sense. There's still the o-ring friction but nothing like the force of keeping a poppet type valve closed, which would mean less force to open it, so the bolt spring might be weak enough to allow for shell ejection and therefore potentially semi/full auto fire...



edit: alternative configuration with greater internal volume:

You would have to reverse the fill plug on the last design.

Oh no it's one of these:



Wonderful things, if only I had discovered them earlier.

Some more idle musings, combining the locked projectile "valveless" design with a balanced spool. The problem with the latter is that even in small calibers, beyond a certain pressure it becomes far too difficult to actuate when made like this, however if you incorporate in a system where the friction is being balanced out in the opposite direction it should make it relatively easy to fire without too much effort.

Something interesting on this subject, there is a company called Inovairtech making Magnum Air Cartridges made for larger bores (0.257"-0.40") with some impressive performance characteristics, exceeding 100 ft lbs of energy for most projectiles.

There is nothing particularly innovative about the cartridge mechanism, it's a balanced spool that is hollow, hammering the base of the spool exposes ports at the rear which allows the air to vent through the hollow spool into the barrel:

[youtube][/youtube]



This is virtually identical to the airsoft APS APM50 cartridges:



The difference is obviously the volume and the pressure, they can take up to 4500 psi.

Another clever feature is the head shaped like a quick connect fitting which allows for rapid filling without the need for a complex fill rig:



Overview of one of their single shot rifles:

[youtube][/youtube]