splitting case necks
This is my first post and I could really use some expert help.
I am slightly new to reloading. I understand the basics, but do not know enough information or have the tools required to find out certain things. I am currently using a .308 Rem. 700 police action on an AI stock. I started reloading 155 gr HPBT with re-15. I have never loaded up to the maximums I have found in all the reloading data I have. this weekend I went out and ran through about 15 rounds and found that 2/3 of the case necks split. Not only this, but at 600 yards my rounds were all over the place. I am not saying I am an expert marksman, but every time my rounds were hitting low. So i would raise my elevation, shoot, then it would continue to be low. at least 7 times I raised my elevation, but still hit low of the target. I pulled one of the rounds when I got home and found that the powder was around 42.6 to 42.8 grains. Can someone just give me an idea if they might know what is happening?