Do you mean the front gas pressure might deform the rear ball to where the rear ball having pressure against it from the front gas, would push the rear ball backward against its charge and possibly push and deform the rear ball tighter against the walls of the chamber, and thus make the rear ball have a tighter seal against the chamber walls that might help to stop the front gas from getting past it to set off the rear charge? Is that what you meant?
no not really . what was commenting on was your drawing . if enough pressure was being applied , then yes IMO that would happen just as happens with the projectile as its in motion and starting down the bore .
in which case yes i could compress the charge .
My other question is, on that double barrel flintlock pic you showed, that seems like it isn't the same thing I was describing. Because the flash channel of one barrel is rotated away from, and closed off from the priming powder. And since the flash in the flintlock's pan is open to the air and not contained, I can understand how that rotating pan would be sufficient to keep the other flash channel away from sparks since the other flash channel in the pan is completely rotated out of the way of the pan's spark, and there is no contained pressure that could force the spark around the rotating pan and into the other flash channel.
But that isn't the same thing as superimposed charges on top of each other. Because then the hot gases and sparks are more contained (than in an open to the air pan) and pressurized and could under pressure squeeze past the rear ball and wad and into the rear charge.
No its not the same as a super imposed charge .
What i was trying to show is that the case doesn’t always goes or get appled as we think .
But think about this . In order for a part to move within another part , what does is have to have ?
Well to answer that , space , it has to be smaller even though that tolerance maybe microscopic . Simply put it cant be the exact same size or it would act as a seal and thus not move ..
Yet in the case of the Knock Pistol , the heat and gas does not flow to the other charge
so was this pricaple new , no . in fact its an old application derived from super imposed loading theroy .
IE take a look at this Jennings 12 shot flintlock which uses 12 superimposed loads
Jennings made a few diffrent rifles and pistols based around superimposed loads
here is a link from a right up in "Guns, Mag "
Hawg's mention of the barrel to cylinder gap allowing bleed off of any overpressure could lessen the overpressure, but the questions are, is it enough bleedoff of overpressure to prevent a bulged barrel or to keep the cylinder and or barrel from exploding? And would the front ball be out of the cylinder and into the barrel before any overpressure occurred? Or would the overpressure occur so fast that the ball would not have left the cylinder before too high of overpressure occurred?
IMO the only way that could happen is if one of the loads was not fully seated thus causing the pressure to achieve a level higher then the barrels ability to contain it . which in turn must accumulate faster then the chambers ability to expand as the projectile moves
now is this totally safe , NOPE.
in fact Bartolomeo Girardoni’s son was killed if i recall correctly , by a repeating type gun . now if that was do to him firing the back charge prior to firing the forward charges , i dont know . but the result was Girardoni designing the repeating air rifles that eventually were fielded by some militaries and carried by Lewis and Clark on their famous expedition
here is an even earlier application.
anyway , my point is that it worked well enough that there are a number of surviving examples from different makers .
like i said before , most likely they didnt catch on because either they were not mechanically un reliable OR the were found to troublesome and thus were not as favored as the revolver applications which did not use superimposed loads