Ray and I disagree about this, at least about the .257. The 7x57 needs at least a 3.1" magazine, but the .257 was designed as a 2.8" overall-length cartridge from the get-go, and works fine in a short action. I have owned a bunch of them, and 2 right now, and the supposed "advantage" of a long action with 115-120 grain bullets amounts to about a 2% (theoretical) increase in muzzle velocity, or about 50 fps with heavier bullets, which means zip in the field. In reality thye variations between different barrels will be that much.
I have always been able to get 2900+ with 115-120 grain bullets even from the short actions. The published +P data will do it these days. If extra velocity means that much to you, why not just get a .25-06 or .257 Weatherby? Those will get a LOT more velocity out of a long action than seating the bullet out on a .257.
The other factor is that standard .257 reamers (and all factory ammo) are set up with a throat for 2.8" ammo. You can get the throat lengthened, but why? Get a .25-06 and an extra 150-200 fps without leaning on the poor little Bob.
