Maybe it will work, but it shoudn't work right.
The 30-30 case is slightly longer (2.039") then the .308 (2.015").
So it would seem it would crimp the 30-30 .024" below the case mouth unless you trim the 30-30's .024" shorter then normal.
Just for general info, the Lee 30-30 FCD collet is part #S13111, and the .308 Win collet is #S13110.
If one collet worked right for both calibers, Lee wouldn't make two different ones.
rc