That's interesting, and something I'd never heard before. My son and I each have a Browning .40-65 BPCR. The chambers are so close that a fired case from either will fit the other perfectly, and the throats seem to be within a couple of thousandths. We have formed brass from Winchester and Remington .45-70 cases, using a Redding .40-65 FL die with no problems. After first firing we have neck sized only using a Lyman neck die. Maybe we've been lucky.
Paul
