Mimimal twist HAS to be a factor with that Texas 25-06. 1 in 12 should help in gaining some velocity. I know Lazzaroni uses mimimum twist on his rifles and they scream. Can't remember where I read it maybe PO Ackley's double book set. IIRC it has something to do with less energy lost due to the decreased twist.
We know bearing surface and freebore also can increase or decrease energy loss which translates into more or less velocity.
