Fly-K mortar - "captive piston" variation

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jackssmirkingrevenge
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Wed Mar 16, 2011 2:15 am

Rheinmetall's Fly-K mortar operates on the same spigot mortar principle as much earlier weapons like the PIAThowever it marries the idea with the captive piston principle to provide a relatively quiet shot:

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With some imagination I think the idea has potential for spudgun applications, something like this:
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Hotwired
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Wed Mar 16, 2011 9:59 am

Also means more weight to carry if the projectile is taking the gas trap with it.

Depends how quiet you want to be.

Certainly a dam sight quieter than my last musings on hybrid launching which was literally launching an open chamber: http://www.spudfiles.com/forums/hybrid- ... t6559.html
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jackssmirkingrevenge
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Wed Mar 16, 2011 1:36 pm

Hotwired wrote:Also means more weight to carry if the projectile is taking the gas trap with it.

Depends how quiet you want to be.
It could be a good project for those with wide open areas to launch over, I certainly don't have the space :roll: I would envisage a parachute and camera...
Had you actually built that?
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Hotwired
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Wed Mar 16, 2011 4:49 pm

Nope.

But going on differences between a closed chamber and having a hollow chamber directing blast back at you. I'd still stand by it being a lot quieter :P
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jackssmirkingrevenge
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Thu Mar 17, 2011 1:48 am

Hotwired wrote:But going on differences between a closed chamber and having a hollow chamber directing blast back at you. I'd still stand by it being a lot quieter :P
Indeed.

The Armbrust also uses the captive piston concept, however this time with two pistons travelling in opposite directions, one firing the projectile while the other fires a plastic countermass of the same weight.

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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Thu Sep 13, 2012 8:19 am

Another interesting "real world" example of the principle, the "Bigot" designed to be fired from a 0.45" pistol:
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Sat Oct 17, 2020 11:02 am

Came across this prototype, looks like the principle is still being examined for hand-held weaponry:



source video

https://www.ploughshareinnovations.com/ ... mmunition/

edit: more here: https://ndiastorage.blob.core.usgovclou ... t19185.pdf

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Image

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https://accurate-mag.com/case-telescopi ... l-systems/
hectmarr wrote:You have to make many weapons, because this field is long and short life
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hectmarr
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Tue Oct 20, 2020 11:42 am

I like the system, I did not know it.
I have a kind of "grenade launcher" that works with a rupture disc, but it is not exactly like the drawing. The projectile is simply housed in the firing barrel. It is an ancient weapon that I built, that I adapted for this purpose. The "cartridge" that houses the o'ring and the rupture disk has no ammunition, and I only use the gases generated at 8X, to propel the self-built projectile, which is hollow. I increased the amount of air, because you need more air to decently throw the projectile. It is a plastic container, about 15 ml, with three fins and a hard aluminum tip. It weighs about 10 grams. I have tried to increase the weight by adding a little lead to the nose, but it seems to be a lot for the little base, and sometimes it inflates it. Besides, the roar is deafening and the ammo is damaged when it hits any target. I have left it at 10 grams and I shoot it against a thick fabric where it does not get damaged. One of the most fun weapons to shoot. I'll add some photos this afternoon.
Ideas don't make holes. The weapons yes! ;)
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hectmarr
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Tue Oct 20, 2020 12:20 pm

This is. I know it is not the same because the weapon has a firing barrel, but it has something to do with it, I think.
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Ideas don't make holes. The weapons yes! ;)
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Wed Oct 21, 2020 6:38 am

Haha very nice :)
I increased the amount of air, because you need more air to decently throw the projectile.
That is usually the issue with this type of setup, a lot of dead volume and small surface for the pressure to act on vis a vis the projectile diameter. Still, it looks like it would be fun!
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Wed Oct 21, 2020 10:34 am

Air at atmospheric pressure within the barrel and projectile appears to act like an elastic. The gases of the combustion chamber compress this air and only then the ammunition survives, and the shot is observed smoother. The air inside the projectile where the force of the compressed air is exerted is about 3.8 cm2. The projectile fits very tightly inside the barrel, so that almost no air can escape.
I have tried placing the projectile 10mm from the rupture disk, and the projectile takes a sharp hit, and appears to fly less. I am burning 10 cm3 of butane and the amount of air in the mixture is about 200 cm3.
Ideas don't make holes. The weapons yes! ;)
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