It seems there are several (3) different chambers for the 6.8 spc that specs are known . Then there are producers that offer their own chamber and don't publish specs. The first chamber developed at remington can cause high pressure due to a short lede and sharp angles . It has been changed . Most of the difference is in the lede . It can restrict bullet weight choice and bullet choice with regard to shape. So which is best and how do you know what you have short of a chamber cast ?