This is the die I cobbled up to perform this enlarging of the cases. Both work perfectly, in a single pass, no annealing, no other steps.

The first die and expander is a .44 magnum expander die,w ith the plunger tapered so it will enter a .30 cal. case.

The second die is an old .308Winchester die that I opened up inside for neck sizing my first 9.3x62, back in 1978. The expander is one I turned on the lathe- it will take new .25/06 or .270 Winchester brass and open them up to .400" in one pass, without case loss. When I necked some old .30/06 and .270 range including pickup brass to .400" with this die, I lost only 7 cases out of 200. Some of that brass (.270 and .30/06) had been fired as .30/06, 5 or 6 times, yet most survived such treatment.