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Coaxil stick rifle breech loading ?

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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Coaxil stick rifle breech loading ?

Unread postAuthor: jakob » Wed Dec 10, 2008 7:06 pm

is it possible to make a breech loading system for a coaxil stick gun or does it have to be muzzle loaded ?
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Unread postAuthor: Gippeto » Wed Dec 10, 2008 7:35 pm

Pulling off an actual breech loading co-ax is going to be a challenge.

I had an idea for it some time ago.

Basically using a doughnut shaped chamber sealing piston, so that the ammo could be loaded through the middle from the rear.

The ammo "tunnel" had to be fixed at the rear of the pilot chamber. The piston in its forward and sealed position, would complete the "tunnel" into the barrel.

The "bolt/ram rod" would hold the ammo in position. This would slide in, with a few threads to hold it.

It required seals on the outer and inner diameters of the piston.

Sorry, no pictures exist to put up.
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Unread postAuthor: MrCrowley » Wed Dec 10, 2008 7:47 pm

I think pimpmann22 tried and failed, IIRC, his idea could've worked. No idea if the topic is even on this website but you could try searching.
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Unread postAuthor: Hotwired » Wed Dec 10, 2008 8:47 pm

Strictly staying to the coaxial design of the barrel being inside the chamber and using a chamber diameter piston/diaphragm...

You pretty much need to remove the whole piston to load.

However if you stray from a full length coaxial you can have the chamber around the barrel stop short of the butt of the barrel and use a loop of fittings to create a standard piston valve feeding from the chamber back into the barrel end, thus leaving a section of the base of the barrel free for a breech load.
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Unread postAuthor: SP00K » Wed Dec 10, 2008 9:01 pm

It is possible. I'm not really sure what anyone was explaining because I have little experience with coaxials, but you could theoretically do it.

If you had a tee pipe that was on the part of the barrel inside the gun, you could have it portrudeout the side of the tank into the open. Thus been said, you could only use spherical ammo. Here's what I'm saying:

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Unread postAuthor: Ragnarok » Wed Dec 10, 2008 9:14 pm

Hotwired wrote:However if you stray from a full length coaxial you can have the chamber around the barrel stop short of the butt of the barrel and use a loop of fittings to create a standard piston valve feeding from the chamber back into the barrel end, thus leaving a section of the base of the barrel free for a breech load.

Personally, and with no offence intended to anyone, I don't see why people choose to do things like this. It's no more than a barrel sealer where most of the chamber is wrapped around the barrel, to no real gain.
It stiffens the barrel a bit from a regular barrel sealer, but you can equally do what I did with HEAL and just tie the barrel and chamber firmly together, and that doesn't cut the chamber volume.

There are a number of reasons to go fully coaxial, and these "half-coaxials" can either be seen as a coaxial with some of the troubles of a barrel sealer, and the possibility to breach load - although still with limitations, obviously the barrel cannot shift around in the same manner as a barrel sealer... or a barrel sealer with some of the troubles of a coaxial.

Basically, whichever way you approach that idea, it just seems to make sense to go wholly one way or the other, with all the benefits and disadvantages of each type.
With current design limitations, that means you either have a breech loading barrel sealer, or a muzzle loading coaxial.

There are ways to breech load a coaxial, one of which is much like the Don Gippeto described, but a half-coaxial is, IMHO, not a true way around the problem.
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Unread postAuthor: Hotwired » Wed Dec 10, 2008 9:41 pm

Coaxials are just not a good path to go down if you want breech loading. The whole principle of the entire barrel especially the butt being within the chamber/valve gets in the way of it.

Anyway, I'm not seeing the issue there with a half coaxial. I did have a design of one a while back but it just didn't fit with what I wanted.

There are a couple of issues they bring from the coaxial side:

Greater weight compared to an over under of same c/b volume/size
Greater cost ditto due to the larger bore chamber costing more
Inability to switch barrels.

But so be it, you now have one tubular section for the majority instead of a stacked pair plus practical breechloading capability.

Unless there is a requirement for a total coaxial cannon there is no problem with a hybrid approach.

The ideas fielded can work but with rather more work required to combat the new problems of sealing and flow restriction.
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Unread postAuthor: VH_man » Wed Dec 10, 2008 9:43 pm

Someone did this once where the piston ran at 90 degrees to the Barrel.

Too tired to make a picture of how it would work..... mabey later.

But basically, the barrel runs along the entire length of the gun, With a Tee placed in it pointing upwards into a Larger tee that the piston sits in. Air is let into the barrel through the tee held inside the middle of the chamber.

Honestly, Do what Rag said, And stick with a Barrel Sealer, Unless Absolutely Neccecary.
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Unread postAuthor: Hotwired » Wed Dec 10, 2008 9:57 pm

Your recollection is one of the ways I was thinking of, the piston either blocks or is offset to one side of the barrel.

VH_man wrote:stick with a Barrel Sealer, Unless Absolutely Neccecary.


A barrel sealing valve and a semi-coaxial are not incompatible ^^

I wouldn't suggest anyone stuck to any one cannon design however ubiquitous that type was. Chap hasn't even said he was going to make a cannon and who knows, there might be a requirement for a coaxial.
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Unread postAuthor: psycix » Fri Dec 12, 2008 6:51 pm

I have breach loaded my coaxial gun all the time.
But that was just because I unscrewed the back cap, took the piston out and reloaded since I was too lazy to find a stick long enough to muzzle load.
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Unread postAuthor: Daltonultra » Fri Dec 12, 2008 8:31 pm

I have a slightly different idea.

Use 2 T's, a smaller inside the larger. The straight-through of both T's would be along the length of the chamber and barrel. The bottom of both T's would go out at the 90* angle to from the piston valve. The rear of the barrel behind the T's would stick out through the rear of hte chamber, with a ball valve ate the end. To load, you open the BV, push your load in through the BV and past the T in the barrel, then close the BV.
Basically, it places the piston at a 90* angle to the barrel, so there is no need to alter the design of the coaxial valve itself.

I'm on my Mom's Macintosh right now. When I get back on a computer that makes sense, I'll draw up a quick design sketch.
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