Originally Posted by KY Jon
Pressure can be calculated by a formula. P is pressure, F is force and A is area. Pressure equal the force divided by the area.

P=F/A

Pressure seems simple to understand as it is the result. Measure the force and calculate the area. Force is the effect of the gasses and shot acting against the barrel wall, the empty shell, the breach behind the shot and air in front of the shot, Area is the volume of space as the gases push the payload down the barrel. So as the shot goes down the barrel, the area increases and this is why we can shoot barrels not as thick as the chamber area, where the volume is smallest and the pressure can be the greatest.This is also why a slow burning powder can have lower pressure early but still achieve a good velocity. They also can have higher pressure down the barrel, compared to a faster burning powder which may peak early and drop off quicker. There are a ton of variables such as how fast a powder burn rate, how hot a primer to achieve quick ignition and full burn of powder, compress-ability of shot, steel compresses less than lead and the amount of compress-ability of the wad which will spread the pressure out a bit by absorbing energy as it collapses. .


Um, no. There is an awful lot wrong with this statement. First off, Area and Volume are two entirely different things. That definition of Force is also incorrect. And nobody is going to be able to calculate the peak chamber pressure or show the pressure curve of a given shotgun shell load by applying this P=F/A formula either. That's why we have to rely upon pressure data from either the ammunition factory, or employ the services of someone like Tom Armbrust, who has the equipment to accurately test shotgun shells. They do not use a calculation to determine pressure. Modern ballistics labs use piezo-electric transducers to read pressure in the chamber and along the length of the barrels. Older pressure guns had a piston that compressed a lead or copper crusher The amount of compression was measured with a micrometer and the amount of compression was converted to lead units of pressure (LUP) or copper units of pressure (CUP), and only told us peak pressure. Here is a pretty good general explanation of old and new methods of cartridge pressure testing:

https://www.shootingtimes.com/editorial/ammunition_st_cuppsireloaddata_200905/100105

And in less time than it took Ed to post this nonsense, he could have simply Googled "convert bar to psi".

Originally Posted by ed good
vatt essen dare formuler, converten dare bars unt tu dare psen unt dare i's...

A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.