Re: Secondary Explosion Effect? Or.....?
That's exactly what I shoot, except that I run Hornady SST's (139gr). I've never had any cases that came out looking like that though. I did try some loads in the 80's, but 90-93 grains seems to work best, for RL-25. Tomorrow I plan on trying out my first RL-33 loads.
The issue that I have found with fresh rem brass, is that there is a "lip" on the inside of the neck, that doesn't want to go away, no matter how many times the brass is run through the sizer/expander die. I have a 3-way cutting head on the trimmer, but the fresh cases come up too short for me to want to trim them, until after they have been shot at least once. Basically, they need to be shot once (fire-formed, if you will), to convert that lip into more length. After that, they become pretty decent brass.
Try working the fresh cases through a sizer/expander die at least a dozen or more times, before they are shot for the first time. See if that takes care of the problem.