Easy enough to test all your copper removal products.
Take a small section of copper pipe from home depot. Place drops of all your favorite copper removers, allow the to sit on the copper pipe for 1-2 minutes, wipe off and view the results.
I tried this years ago and KG12 had the best results
Witnessed this failure a couple of years ago. The shooter had minor bruises to his face and slight concussion, eye protection save his vision .
We verified no squib load or obvious barrel blockage.
Rifle was a 300WSM. Factory loads. He had fired 2 rounds, second round caused the failure. He...