I have some once fired factory 257 Roberts cases and no longer have the rifle. Need your opinions on Full length resizing and Necking Up in my 7mm Mauser dies. Cases will be trimmed and measured as required. OK to shoot in my 7x57???
I know the 7 x 57 is the parent cartridge to the 257 Roberts. Most discussions you read about are necking DOWN the 7 x 57 to 257 Roberts. You never hear anything about necking UP 257 Roberts to 7 x 57. However it makes sense it would work just curious to see if anyone has any opinions on that. 257 Roberts has a different shoulder angle than the 7x57 however that should be taken care of when resized and necked up to 7 x57. Thanks !
You’re right. Shoulder angle is the same. I meant to say the shoulder length on the 257 RBis is longer than the 7x57. Should all come out ok after resizing and trimming. Might need to check neck thickness though.