As many will know, i have a habit of thinking outside the box, mainly just to work through something and see if it can be done.
Anyway, so i was working through one of these projects and i got thinking of case neck thickness.
When a cartridge is fired the case obturates, sealing the breech from gases that may attempt to go backwards towards the shooter. This is mainly done by the thinner neck section of the case.
Generally blackpowder cartridges were very thin and when the transition was made to cordite these cases (with cordite loads) stuck somewhat causing extraction issues in falling blocks and double rifles. The solution was thicker brass.
But how thick can you go before it stops obturating? Obviously pressure will have a huge impact on this but lets go to extremes here and say 3mm wall thickness and 30,000 psi.
Anyone know the formula i'd be best using and the values for cartridge brass?