I have been reloading for about six months. Started out witha 40 s&w in a baretta px4. All loads function very well. There only three incidents of failure to load. Recently Started loading for springfield 1911 gi. Loads were; 4.5gr of universal powder, 230gr casr round nose. Reloads WERE firing well.Experienced a couple of hot rouns. A good friend wanted shoot some of my reloasd in his 2 week old Kimber Custom. Big bang from his Kimber on about the tenth round. Powder marks on both hands. Small debris scratch on his face. Thank god for good eye andear protection!! Shell casing jamed in gun. Bullet did clear the barrel. After disassembly of the Kimber I removed the Shell casing. Ruptrued at the base. Blown out half way round. No damage to firearm. My friend is unharmed. What caused this. I'm loading on a Dillon Square Deal. CCI primers, COL 1.24. I am checking the first ten rounds at the start of a load session. With powder charge set @ 4.5gr my powder checking showed only two rounds with powder weight @ 4.4gr. Loading is very dependable. I continue check. every tenth round. My concern is with the crimp. What should the crimp measure be? I feel that the high pressure was caused byexcessive crimp. Is this possible? Have bee using mixed head stamp cassings. This incident was with PPU brass. always load with factory recommended starting chargs. What shell casings are most dependabled. And what casings should not be reloaded. Thanks in advance!