Gene,<BR>The Quickload program I have lists the 257 Improved.If you wish to send me info by e-mail regarding case dimensions,which bullet and powder etc. I can run it through the program and send you a printout of pressures with varying charges of a given powder, along with corresponding velocities for those pressures.Should help you determine about where you are.My email is cornellmontrose.net.Regards,Frank.