I put together a 6.5x06AI for my nephew with a older 700 action and 8tw.proof med.sporter 26" steel barrel.
Its and absolute hammer out to 1,000 with H1000 cci250 and Berger 140 at 3150fps.
I tested it between RL26, H1000 and Fed 215 and CCI250 primers and H1000 and the CCI250 won out the vertical was alot better.