Was loading some +P 9mm for a new R51 pistol I had picked up the week before. Had an established load that tested safe in the pistol a couple hundred times. Went from single stage to a progressive and ended up loading a few 380 cases with the +P load.

The first HOT 380 bulged at the unsupported barrel ramp then the brass separated at the rim. Luckily, Remington's Aluminum frame directed all that excess gas down the mag and out the bottom. I did catch some black stuff that squeezed between the grip and frame on my hands though. No injury, washed hands and went through 250 rounds to find 3 more +++++P+++++ .380s

A good painless lesson.