Powder markings inside fired cases

I no this is no great observation on my part and most have probably seen this before but I thought it was pretty wild. I noticed the inside wall lining of this fired 40mm case had the imprints of the powder left on them. The cool thing is when the multi-perforated powder grains were at a 90 degree angle to the side wall of the case it clearly shows the perforations. I am not 100% sure, but this looks similar to the physics of a hollow shape charge principle I saw on Future Weapons??? I forgot what they called the principle, it was named after the scientist who discovered it. I could be way wrong?


Munroe effect.


That’s a very interesting thing you show there. I’m not familiar with that being visible in regular brass cases. What is the case (40mm L/70?) and is that a liner of some type of polymer?

I think the Munroe Effect is the result of reflecting waves in detonation, probably not at velocities of detonation below like 3000 mps, and is something you don’t want going on in your average gun chamber.

Probably in this case the forces are heat (flame) and pressure rather than shock wave.


Rick you are right as I was totally thinking the Monroe Effect, thanks! Dave, I think you are probably correct about this phenomena not being caused by the Monroe effect and more to heat / pressure forces; but really I have no clue :-) This particular case is steel but I am not sure if there is a liner of some sort?