1. Try the CCI BR and BR4 primers, they are harder. Is this a 700 action w/o a bushed firing pin. Most 700s have to have th firing pins bushed to push the BRs.
2. Look at www.6mmbr.com
and their 6mmBR tests, might want to look at RL15 powder. Plus they have an article I believe on the 22 Dasher.