A Few Ideas...

[Crna Legija]

wouldn't the second ignition put at least half of its energy into pushing the piston backwards rather than the projectile out of the barrel as the area behind the piston only has whatever pressure the ignition of the 20x gives and the detent in the barrel would have to be at least more than that or the projectile will leave the barrel before the second mixture diesels

The man makes a good point, a heavy piston is a must.

or

[jackssmirkingrevenge]

or

At which point it really is getting too complex for its own good.

[POLAND_SPUD]

or just build a high mix hybrid

[Fnord]

edit; oh and poland, the only advantage here is that you could used shop pressure (say, 10x) to get 100x-plus perfomance. This would be good for the average spudder but may be difficult to do with off-the-shelf stuff.

Although an internal detent could be used, it would get sheared off neatly unless it was really strong. It is also a bad idea because you need orings on the piston. A detent could damage them or at least keep them from sealing as they pass over.

I don't know if auto ignition temperature would be reached- certainly not by the ignition pressure alone but perhaps with the stored kinetic energy of the piston. If not, no big deal- just add some springy electrical contacts at the front of the stroke and let the piston run into them. You could hook up a couple camera caps, and the contact arcing would be good enough to ignite the mix.


-------
Seriously, I don't want to stop anyone from attempting it, but I had this idea in like 2009 and didn't even bother to say anything because it was so over-engineered/complicated
good luck!

[saefroch]

Crude adiabatic gas law calculations say that you'll exceed the autoignition temperature of the secondary chamber by a factor of ~2.7. Honestly... that's a pretty safe margin, I'd say anyone with the supplies or desire should try this.

This system may work very well if you have a burst disc or a detent holding back the main valve from opening until after combustion. If you can manage that and also restrain the piston from just absorbing the energy and recoiling, this will work.

[Crna Legija]

Although an internal detent could be used, it would get sheared off neatly unless it was really strong. It is also a bad idea because you need orings on the piston. A detent could damage them or at least keep them from sealing as they pass over.

If you look closely in my edited pic, theres a little cut in the piston. it should stop right there.

[shiny455]

At which point it really is getting too complex for its own good.

yes i agree and i believe there is a good chance whatever you use will just break under the pressuret.. also with what i said earlier as the surface area of the piston is greater than the projectile wouldn't this effect be increased a lot.

[hectmarr]

Using two cameras interconnected by a small hole, one large and the other small, more compression can be achieved in the second chamber, the smaller one, in a simpler way to build. The two chambers are filled with the same mixing pressure, and the electric igniter only goes in the first chamber, the largest one. In combustion weapons at atmospheric pressure, it works, significantly increasing the energy of the small projectile. It's just an idea

[hectmarr]

This would be the system.
The fuel mixture in the two chambers has the same pressure. When camera "A" explodes, , and the pressurized gases further compress the mixture in chamber "B". It is the simplest thing to fill the two combustion chambers without complicating much what I already have manufactured. It is autonomous hybrid 6.25 caliber fired with this method.
An intermediate or more basic test option may be to fill chamber "A" with pressure mixing and chamber "B" with mixing at atmospheric pressure. In this way you do not have to add the rupture disc (orange), although the increase in power should be less, without doubt, but easier to do. In this case, the same firing barrel acts as the "B" chamber. I had to put the ammunition in half approximately. The ammunition closes almost hermetically the firing barrel
I failed to explain that when the piston opens the transfer hole, when some mixture escapes the shotgun, the pressure drops a little, but enough for the piston to close the hole again and the mixture remains retained in the main chamber, "A".
You can try not to miss any of the mixture in the diagram that has the spring piston. (It is a cycle of pumping less, nothing escapes towards the firing barrel), and put there a little oil as dieseling. The gases that escape from "A", should ignite the drop of oil and compress the air lodged in the back of the ammunition ... I will try to test to see if there is any increase in energy, but I do not know.