Big problem with my brass need help!
I just finished resizing my brass with a lee collet necksizer and found groove marks on my belts on the 7mm mag nosler brass, some of the groove marks are way more evident than others, meaning you can see and feel them with your finger much more. They metal snags on my finger a bit from how rough they are. This was the 4th time they were fired, I annealed them on the 3rd. When I was at the range the temp was 75 degrees. My load is 70grs of RL-25 with a 160 accubond my avg speed is 3077. I have shot this load over 300 times with out a problem like this, but maybe not at 75 degrees, but I have shot it at 70 degrees many times with out a problem.My measurement on the belt is .530" it seems fine compared to my twice and 3 times fired brass. Now has anyone seen these marks before and what caused them I am stumped? That day I fired 30 rnds 6rnds per target on of my targets was a .860" for 6 shots in a gusty day, the rest were average between 1.5-2 inch groups.