Hi, new here, I recently acquired a rifle from my deceased uncle, a sporterized Japanese Arisaka, rechambered in 6.5x257roberts. From comparing the brass that came with the rifle, 257 and 6.5x257 are pretty much the same except the mouth is opened up to except 6.5 cal. Would like to reload some newer brass, but was thinking all I need to do is fire 257roberts cartridges and that would form the brass to 6.5x257. I found a box of new Remington 257 Roberts at a recent gun show, I'm pretty sure this will work, but is this the right way and safe way. I have a set of RCBS dies (6.5x257) that came with the rifle. Does anyone here reload for this caliber?? Appreciate any info I can get, rich