There were a couple of threads several months ago looking for a commonly available die that would allow neck sizing of the various 450 BPE rounds without overworking the brass. I put it this way in one of those threads:

"What I am looking for is a die that I can neck size various old .45 cal black powder express cartridges that won't overwork their expensive brass so much. For instance, the RCBS dies for .500/.450 No.1 2-3/4" Black Powder Express that I have will reduce the fired case neck diameter so much as to almost hold a .440" bullet. Doing that and then opening them back up to easily seat a .460" paper-patch bullet is positively criminal considering the $5 apiece for cases. A neck size die that would give my brass an outside neck diameter of about .485" would be perfect."

Well, I'm happy to report that I have found the secret die that does this well, namely a Lee factory crimp die for the .45 Colt. The design of the Lee factory crimp die includes a sizing ring at the entry to the die that's supposed to smooth out any case mouth bulging after over zealous crimping. It turns out that the diameter of that ring is just about perfect to neck size fired 450 BPE rounds to snugly fit paper patch bullets. Works for me.

One more from the (BP) lunatic fringe...