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Auto-loading shell theory

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: trollhameran » Mon Aug 18, 2008 4:22 am

This is an idea I just came up with whilst thinking about the falling block design.

Its easier to just look at the picture to see how it works rather than me trying to explain, and if you don't understand anything or have any questions, just ask.

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Unread postAuthor: POLAND_SPUD » Mon Aug 18, 2008 5:36 am

I see one serious problem here....

when the sabot is being fired air will go to the magazine (thus producing dead space and lowering performance + possibly causing jams by moving remaining ammo) and some of it will leak through the the bottom
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Unread postAuthor: trollhameran » Mon Aug 18, 2008 5:47 am

That is very true, It could possible be solved, or at least reduced by having rubber on the ends of the shells to minimize air loss, and then have springs in the magazine to counteract the increased friction from the rubber.
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Unread postAuthor: POLAND_SPUD » Mon Aug 18, 2008 5:59 am

I mean that when the sabot starts moving there is nothing that blocks the magazine tube from the barrel (and pressurised air). So some air will leak into the magazie and rubber ends won't help
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Unread postAuthor: trollhameran » Mon Aug 18, 2008 6:35 am

Ahh right now I understand, I didnt think of that :? I can probably make a crude knockup of it in about half an hour, so maybe ll go try it and see how bad the air loss is, because if its alot then its not worth doing because ill lose alot of power.
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Unread postAuthor: kablooie » Mon Aug 18, 2008 2:54 pm

Also I see a potential problem being that the weight of the shells in the magazine could slightly bend the sabot (unless it was really tough or something) and make you lose more power. Both of the problems that POLAND and I present could be solved by having a teeny (like two shot) sealed magazine. But then it might not be worth it...
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Unread postAuthor: trollhameran » Mon Aug 18, 2008 3:36 pm

The sabot would probably be made of something like cardboard, as it is cheap easy to get, so I think it should be able to hold the weight, as it will have extra strength from the ammo inside, and copper is reasonably light in small sizes. But I think your second suggestion is definitely worth looking into, a small sealed magazine would almost certainly solve the power loss problem and I could make it around four shots, so as to make it worth having the system on the gun. I am also thinking, maybe have a slide on the bottom with a handle which would be opened after a shot to let the cartridge out and would further reduce the air loss by completely sealing the magazine.
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Unread postAuthor: psycix » Mon Aug 18, 2008 4:07 pm

To avoid the sealing problems, you may use it in combination with a blow-forward bolt. The bolt simply shoves in and seals stuff of with o-rings.
Using this design, it makes it possible to use longer ammo than just spherical with a blow-forward.
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Unread postAuthor: Brian the brain » Mon Aug 18, 2008 4:18 pm

The blow forward valve already does not require spherical ammo.
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Unread postAuthor: trollhameran » Mon Aug 18, 2008 4:31 pm

All the ideas your coming up with are great, its summer holiday, I got loads of time on my hands so I will try to test out all of these ideas, Im really liking making different magazine mechanisms at the moment :D
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Unread postAuthor: trollhameran » Mon Aug 18, 2008 5:04 pm

Ok I have had yet another idea :roll:

What if you cut a breach slot out the bottom of the barrel, then have a sealed magazine underneath, with the saboted rounds in it. These will fit snugly in the barrel. Then a spring pushes the rounds into the breach, and when one is shot the next is pushed into place. Obviously the sabots would have to be relatively strong due to the forces from the spring,but this would get rid of the need for shells, which need to be ejected.

The magazine would be as air tight as possible but still be open able, so that new rounds can be loaded, and also completely removable to allow a standard breach cover to be fitted for when you want it as a single shot gun.

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Unread postAuthor: psycix » Wed Aug 20, 2008 7:27 am

Brian the brain wrote:The blow forward valve already does not require spherical ammo.

But the magazine for non-spherical ammo can be quite hard to make, while the spherical ammo mag can be just a pipe.
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