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Interrupted Screw breech loading

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Interrupted Screw breech loading

Unread postAuthor: Bando_Red » Fri Nov 14, 2008 12:58 pm

has anyone tried an interrupted screw loading system?
It seems like it could be fairly easy to make one from threaded pipes with a couple of hinges,but I"m not really an expert on making things...not take up ridiculous amounts of space.

http://upload.wikimedia.org/wikipedia/c ... inna_2.jpg
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Unread postAuthor: starman » Fri Nov 14, 2008 2:01 pm

You could, with some effort, grind down the threads on a cleanout and cap to simulate this action. The problem I believe would be sealing and less holding strength.

All of the threads are needed to seal properly in an NPT screw connection. If you gap out half the threads, it won't be airtight any longer. Still if you could find a way to seal the openings, this could have promise with a little tinkering.
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Unread postAuthor: jackssmirkingrevenge » Fri Nov 14, 2008 2:39 pm

A not as realistic in terms of artillery but just as quick to open and close and much easier to make would be a cam-lock fitting.
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Unread postAuthor: Bando_Red » Fri Nov 14, 2008 3:44 pm

jackssmirkingrevenge wrote:A not as realistic in terms of artillery but just as quick to open and close and much easier to make would be a cam-lock fitting.


I don't really know much about the cam lock system,but from what I've heard its fairly complex.Of course I've just been browsing the wiki.
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Unread postAuthor: FishBoy » Fri Nov 14, 2008 4:03 pm

Cam-locks are actually quite simple, you flip the lever, and it comes unatached, stick it in a and close the lever, and its sealed
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Unread postAuthor: jackssmirkingrevenge » Fri Nov 14, 2008 4:29 pm

Bando_Red wrote:I don't really know much about the cam lock system,but from what I've heard its fairly complex.


Not at all, take a look ;)
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Unread postAuthor: starman » Fri Nov 14, 2008 5:09 pm

I'll include a requisite posting of my usage of cam-locks and optional masking tape burst disk. Cam-locks are close to a perfect application considering they are an off-the-shelf product. Better, for purpose products could be machined of course.

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Unread postAuthor: taytayswims » Fri Nov 14, 2008 5:21 pm

one of my frineds and i have tried this with an abs end cap and female threaded end and let me say it is quite a task to do by hand with sub-par results. possibly if you had access to the proper tools you could potentialy make a good end, but it takes ALOT of time and precision.
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Unread postAuthor: jimmy101 » Sat Nov 15, 2008 11:21 am

You might be able to get it to work. How well it works will depend a lot on what type of gun it is. I assume you mean this for a combustion. Since combustions really don't need to seal all that well I think it has a fair chance of working. A combustion that leaks at 5 PSI/second will work just fine, a pneumatic that leaked that fast would suck (blow?).

You might consider trying to get the sealing surface to be something other than the threads themselves. Perhaps build up the stop ridge inside the female fitting a bit, adding a thin gasket, and then have that seal against the end of the male thread. The seal is before the threads so the threads don't have to fully seat and and don't have to seal.

To build up the stop ridge you might be able to take a piece of pipe of the same nominal diameter, slice a short length (perhaps 1/4") then cut the ring open (so it looks like a C). Size the cut so that the C can be compressed and fits perfectly inside the female fitting without any gap. PVC glue it in place.

A 1/4 turn breech plug would be pretty cool.

Might want to thing about the strengthen of it though. A 3" plug in a combustion with a jammed round in the barrel will have (3/2)<sup>2</sup>Pi(120)=850 pounds of peak force on it. A normally operating combustion will have about half that force. Is the male thread strong enough with half of it's threads removed?
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Unread postAuthor: daccel » Mon Dec 15, 2008 9:56 pm

The same principle would make a good bolt action receiver for a combustion/hybrid cartridge.

It would be challenging but much easier than trying to make lugs.

Edit: And would get around the sealing problem - it would only have to contain the force.
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