I went shooting two days ago, I brought a Colt AR-15 H-Bar and a Wby Vanguard .300 WM. I was shooting the AR at 100 yards, I loaded 5 rounds in the 30 round mag (can't shoot more than 5 at a time at this range) I shot the first round with no problems, the second round I just heard a click. I thought great, I have a misfire. I pulled the bolt back to cock it again, then I pulled the trigger and heard another click. I was getting frusterated at this time so i popped the mag out and didn't really find andthing wrong. Again I pulled the trigger and had the same problem. I pulled the mag out for the second time and pulled the bolt back to find a .223 case severed in half like a wine bottle, (around the circumfrence not from neck to flachhole)the case had a clean cut about 3/4 the way down. I pulled that out and put the mag back in and pulled the bolt back and heard another click. Getting aggavated I again pulle the mag out and opened the bolt, the round that flew out was about 3" long. The front half of the case that broke in two was stuck over another new round and was being jammed in the chamber. I thought what the hell is going on. I took that other part of the case off and finally fired the remaining rounds. I guess the first round I shot blew up inside the chamber and cut the brass almost perfectly in half. The ammo I was using was Black Hills 68 grain heavy match. The last time I heard of something like that happening the rest of the rounds blew up in the mag and sent pieces of the action into the shooters face. Is this bad ammo because some other rounds look like the brass has a discoloration in the same spot as the one that blew??? Can someone shed some light?