I have a new Christensen Arms 300 RUM. Every once in a while I get a shot with a ejector mark. Primer never flattens. I am shooting new nosler brass. Federal primers. 95 grains of retumbo. nosler 180 accubond. Im not resizing brass at all. Im shooting between 3220 and 3265 fps. I shot 9 shots today and the very first one came out at 3222 fps and showed a good impression of a ejector mark. The rest were fine. I checked over all length on ever shell before I took to range. I double weighed all my powder. They were all the same. The bullet is .024 off the lands. This is brand new brass from nosler. I was having same problem with there old brass and they sent me new brass. Im at the low end with retumbo. My velocity's are not extreme. Why am I having this problem. HELP!