split chamber - possible?

[Kaylee]

Ignore for a moment the "why?" question...

If you wanted to extract a cartridge off the case mouth or shoulder rather than the rim, would it be possible to split a chamber longitudinally and pull half of the "chamber" back? Or perhaps more accurately I should say, have a bolt extension, the inner surface of which provides a "chamber wall" on the inner surface, enter the chamber proper?

Or are rifle-level chamber pressures high enough that such a contraption would effectively expand the "bolt extension" and lock it against the outer chamber wall?

-K

 

[taliv]

i don't see why it wouldn't work.

 

[musher]

Maybe have the sliding joint a dovetail or something like that to provide some strength against spreading the joint and to retard any gas flow.

Then just keep making the assembly bigger until it's strong enough.

 

[db_tanker]

I could possibly see somthing set up with a straight pull action type...locking lug/s would be put into place when the bolt was pushed forward and locked...similar to say a Browning T-bolt?


The biggest issue would be the feeding off the magazine...of course, you could go with a Krag/Jorgensen side mag or just make it into a single shot.

I could also see a Mauser style ejector...

I am guessing you would stick with a full bolt face and a partial lip to help with positive feed...

Neat idea.

D

 

[1911 guy]

Repeatablity

Unless you had some sort of camming mechanism to provide a repeatable lock-up, you'd get a different chamber every time, for all practical purposes. This would make accuracy a very real problem. The pressure would also exert force on the mechanism, making it harder to open after the shot. Current bolt designs don't bind up because they don't have to hold the pressure laterally, just on the case head and with a double lock to ease friction stress on what would likely have to be a single locking mechanism to keep it from being very bulky.

 

[Owen]

To make sure I have this straight, you want to have a longitudinal cut the length of the chamber. During the extraction phase, you want half of the chamber to move to the rear, to extract the casing.

I think the problem would stem from cartridge brass extruding into the cut. You could definately make it strong enough to not expand the split. Just make make the bbl ext. big enough.

 

[Kaylee]

Hrmm.. cool - it might work then.

Owen, yes, that's it exactly. Except the brass part. See, I was wondering if such a contraption would work to feed and eject something like this:

(image from "Matsucorp")



What would be necessary to ensure consistent lockup then? Would say a rotating locking collar or a HK roller-lock type lockup be sufficient?

 

[Owen]

I figured you were working on caseless stuff.

I think the issue would be how to seal up the chamber. at the pressures and temperatures in a rifle, gas cutting is going to be an issue.

Making all of the clearances tight enough to get a good seal is going to take tight tolerances, and will probably make the weapon very suscptible to dirt.

 

[JesseL]

I thought most firearms built to use caseless ammo don't have any means of extraction. After all, what would you need to extract?

I suppose it could be an issue if you wanted to clear the weapon without firing it?

 

[Kaylee]

Yeah, I'm a geek.

Not "working on" so much as wondering "could it actually work, and if so how?"

Hrm - so you're saying the gas would want to escape through that long cut, and basically turn into torch cutting at the surrounding collar?

Ech.. is that a materials issue?

I see what you mean about the clearances issue... perhaps "sand cuts" on the outer face of the bolt extention to "sweep" crud somewhere less important than the chamber? How much fouling do the various caseless compositions we have so far create anyhow?

-K

 

[Kaylee]

Jesse - yup.

That and clearing out misfires.

 

[JesseL]

If I was working on a caseless ammo gun, I think I'd start from a whole other angle. I wouldn't make the chamber part of the barrel at all.

I'd go with multiple revolving chambers, some sort of bastardization of the Dardick mechanism with a Gatling gun. If it was designed right it could even keep going with a dud stuck in one chamber. It would also reduce one of the common, but lesser known problems of caseless firearms - retention of heat in the chamber.

 

[Vern Humphrey]

You might consider something like the Dardick. That was a revolver with wedge-shaped chambers cut from the side. Looking at the cylinder from the rear, it looked like a pie, with three pieces cut out.

The cartridges were inserted into triangular cross-sectioned lengths of extruded aluminum or nylon. When seen end-on, they looked like a wedge of pie with a hole in the middle. When the "trounds" as the rounds were called, were fed into the path of the cylinder from the magazine, they fit neatly into the wedge-shaped chambers. When a chamber was aligned with the barrel for firing, the two sides of the chamber and the topstrap formed a complete chamber.

 

[Afy]

Look at the HK G-11 for ideas as well.

 

[the naked prophet]

Kaylee, look into "transformation toughened zirconia" or TTZ. It's a very new, and very expensive, ceramic. 10 years down the road, it may be only twice as expensive as steel. It can take high temperatures and abrasion without any erosion, deformation, or chipping. I'll bet that would work for your chamber.

 

[JesseL]

You might also consider that the chamber for a caseless cartridge doesn't have to be especially tight.

Conventional chambers have to support the brass enough to prevent it from stretching past it's elastic limit and rupturing, resulting in hot gas leaking from the chamber.

Since a caseless chamber must be sealed in and of itself, without brass, you can make it somewhat looser to accommodate whatever crud might collect there and still have reliable feeding.