No experience with s&b 7x57, but experience with 762x54. What I've done in past is pull existing bullets, dump powder. Charge with my powder of choice, seat bullet of my choice. Fix any bullet runout to ~0.003" or less. Shoot.
Then use the s&b case like any other. Not the same as a Lapua case, but serviceable.
Of the loaded ammo I pulled bullets from, I measured ~0.2 gr difference in weight case to case. Not too bad.
