The 257 doesnt have near the velocity nore the energy the .243 does. Everyone has their favorite calibers and mine is the .243, with the right shells and velocity' s over 3000 fps and the tendancy to drive tacks its a hard gun to beat. At 300 yds its still carying a velocity of around 2400fps. Even claimed by some to be one of the best drop' em in there tracks calibers. I have taken lots of deer and hogs with this caliber. Shock value is what drops deer and this gun has it.
You should see the devastion inside the cavity of a deer that has been shot there, it actually liqufies the lungs. I shoot the Hornady' s in 100 gr and is sighted in at 200 yds with about 1 inch groups at that distance. I have had complete pass throughs on big hogs at over 200 yds away with this bullet. Nothing has gotten away from my .243 , nothing has gone past 50yds if they didnt drop right there. The available ammo for this gun is extensive, you can choose from 55 gr for varmints that shoot over 4000 fps or you can go with 85 gr hollow points from federal that blow huge holes in deer or go with Hornady' s that have controlled expansion for large game. Remington has a new cartridge for it, a 90 gr scirroco bonded that suppose to be awsome for big game. I will be trying them soon. This gun shoots as flat or flatter than even the 25-06 . Its an awsome caliber go with the .243.