Found this on 24 Hour Campfire; why you cant use .30-30 to make .303 Savage. I was close but no cigar, LOL!
1)
wheThe 30-30 brass is narrower at the base, which means it's going to expand by .02"n you fire it risking case failure.
2) The 30-30 brass is .02" longer, meaning that if it even chambers it very likely will be up against the rifling and could crimp the bullet in raising pressures.
Even if resized, the .02" difference at the base would keep me from EVER using 30-30 brass in a 303 Savage rifle. It's just not worth the chance of serious case failures.
30-30:
http://i29.photobucket.com/albums/c2...winchester.jpg
303 Savage:
http://upload.wikimedia.org/wikipedi...303_Savage.gif