Just to back up what other people have posted, if a .257 won't shoot well with a 100-grain bullet and 46 grains of H4350, then there's something wrong with the rifle. I've loaded for about 12-15 .257's and the only one that wouldn't shoot with this load was a Ruger No. 1B with a very long and loose throat.
This is by no means a maximum load, usuaally getting 300-3100 fps dependin on barrel length, but with the right bullet will kill any whitetail or mule deer quite handily.
Have you found that you have to reduce that load with "+P" brass to get the same velocity/pressure?
If I understand correctly, the +P brass is thicker and has slightly less capacity.
