I haven't found that to be the case with the cartridges that I have loaded with both cases.With the 7mmremmag,30-06,300winmag and 338winmag,the winchester cases have slightly more volume and produce less velocity than remington cases using the same load.I have only used remington cases with the 7mmstw.And I too question the use of 4064 in the 300winmag.It certainly is not one of the better choices if you want to see the true potential of this cartridge.