POLAND_SPUD wrote:ohh come on, 1/8" or 1/4" fittings are not that large... personally I think it would be a better idea to build an all metal contruction... probably it owuld be the best idea to combine both threaded and soldered fittings
I feel quite safe with current construction, and the whole point of having "no burst disk" seals is to avoid threaded fittings.
if you're firing at 10x your spark gap has to be 10 times smaller than the outside gap to have a lower resistance so you're probably getting close to the limit
Fair point, we'll see how well it works in practice
edit: sadly, your prediction was correct - while it was ok at atmospheric pressure, when pumped to 75 psi for a 6x mix, the spark arced externally to the schrader
so it seems my visions of a rifle sized cartridge are a little optimistic if schraders are to be used.
On the positive side, when set inside a 6mm brass tube instead of being cast directly into the epoxy, the seal I was using is happy to hold a 4.5mm at at least 100 psi, meaning that it should be good for an 8x mix.
Back to the drawing board...
edit 2: I took this cartridge
, cut it down to 2" (now that I have relaible ignition and a good seal, I can afford to lose some chamber volume) and fitted a seal for a 0.177"BB, testing this evening and if all goes well I'll make a breech/barrel setup to evaluate performance.