I also just recently found one of those. Most likely at the same range. I thought someone had tried turning the neck down for some odd reason. Threw in the garbage without really giving much thought.
Notice the neck length is different between them? I'd say someone is trying to reload without trimming cases and doesn't have the seating die set any where near where it should be.
looks like what the hell u shooting . if i found that id just scrap it for the brass and move on .. unless i could cut it off and make 300BO from whats left of it .