Notice the shiny ring around the entire circumference of the case just forward of the extractor groove?
Cut a case in half lengthwise and you will likely see the the case is thinner right there. In other words, it will appear as a ring on the inside of the case.
This is evidence of excessive case stretching.
The barrel either has excess headspace, or the cases were trimmed too short. (Most likely the former.)
Combine that chamber, and this will happen.
If the gun fired out of battery, there'd be evidence of primer setback.