I have a Lee #2 and it will do my 7x57 stuff, but I have not tried Sellier and Bellot.
I did have that issue you have with the 6.5x55 Sellier and Bellot though: - possibly you have the same situation in 7x57.
Most of my 7x57 reloading was with Highland/PPU. Try that, I am certain it will be fine. It's better brass than S&B anyway.
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