I have never measured it but I use both with the same load data. I will try and measure some today and let you know. If you want to save some money 264 win mag, 7mm rem mag and several others can be made into 257 wby by running it through your die. The necks will be .049" short but as bad as the 257 wby stretches necks they will be close after a couple firings. I have done that often with no trouble. Also Remington did make 270 wby brass and that is identical except for the caliber. Again, just run it through your die. If you are buying brass I would get the right stuff to begin with. But if you have some of the others lying around they will work.