06-05-2011, 12:46 PM
I had to recently pull out of a competition because of this exact problem. Upon investigation, I found that 4 of my rounds did not have the shoulder bumped back enough. I bump my fired brass back .003. These were only .001. I have also found, at least on my G's, that they are not very forgiving about the shoulder not being back enough. I use AA and Hornady 6.5 brass and always full length size my new brass. I do not shoot fire-formed 7.62x39, but the shoulder issue should be similar.