I have the 6.5x.257 Ack. Imp.
My personal data would be slightly strong for the standard 6.5x257. However, the 5th Edition of Hornaday's Handbook or Cartridge Reloading, pg. 235 to 237 has listings for the standard cartridge, in bullet weights from 95 gr. to 160 gr.
BTW, CBBob - Welcome to TFF. Please feel free to join us in all the other forums here on the board.