Just got a Cooper 280 AI, and a nice Redding Deluxe Die Set (40 degree shoulder) and a new box of Nosler brass. So decided to make a modified case as part of my reloading prep. All went well but I deformed the case a bit tightening the jig, wouldn't chamber, so set up my new full length sizing die, added some lube to the case and ran it through. Afterwards had a completely unusable case with the dreaded donut. Not just a bit, but looked like the die shoved the neck down hard and there was no shoulder at all. The only time that's ever happened to me was when I ran the wrong case into the wrong die. Not sure what to think now. Didn't want to run another case through, being a bit stingy with those expensive cases, so I heated up the donut case and pulled the neck out with needle nose pliers while heating it with a small torch. After making it look like a half way normal again I cleaned and lubed a tad and ran it through again, after making sure I had followed all proper die set up instruction. Same thing, smashed neck down into case and created a donut.