I was shooting a number of drills today with a friend and using commercially reloaded 40 S&W ammunition in a P320. When I fired one shot in the middle of a continuous string of rapid fire I had the vague impression of things flying at me and I was hit all over the face with a large number of unburned powder particles. I was of course wearing protective glasses, and the particles hit with only enough force to startle me.

Otherwise the shot seemed to be normal, and I finished the string of fire and the gun cycled normally. After shooting I made a brief effort to see if I could spot a cartridge case that might have been involved, but nothing stood out among the many others in the mud and snow on the ground.

Over the past 60 years or so I have fired many tens of thousands of rounds of various types of ammunition, including a couple of thousand or more of the exact same load, with a large variety of guns, and this was the only time something like that ever happened to me.

Since then I’ve been trying to imagine what could have caused powder blowback like that without something else that would have affected the shot or gun operation.

Any ideas from the group?

Partial separation of the case near the base, not total separation obviously as the extractor was still able to clear the case? Maybe allowed some powder to escape as the barrel unlocked and started to eject the case. Just throwing out ideas.

I had a case that partially separated near the base but it didn’t exhibit the same symptoms.

quote:

Originally posted by SigM4:
Partial separation of the case near the base, not total separation obviously as the extractor was still able to clear the case?

Possibly. I wish I had been able to find the case.

Sounds like a split case starting at the case mouth. This allows just enough gas to escape out the back to cause what you described.

I process over 100k pieces of range brass a year, and of the major calibers I see more split cases by FAR in .40S&W. Like, for every 20 split .40S&W cases I might find one split case for 9mm or .45acp.

Thanks, Fuego220, that would explain it, I believe, and could definitely be anticipated with reloaded ammunition even more than a case head rupture.