Rell,
Let me say first that "500" is giving you sound advise. JJ used my .375 flange to build the first 450/400 rifle for Chapuis ,to check the viability of building the 450/400 on a smaller action than their .470. I bought the BBL's when JJ was finished , I also worked up a load to duplicate the Hornady Load . However , I used Woodliegh bullets. Chapuis wanted to offer a 450/400 that would be regulated for factory ammo and they chose the Hornady ammo (not me). Most of the work was done at 50 yards (not 100). I'm out of the Country right now , but will be glad to send you my load when I get back home. My load will cut a ragged hole at 50 yards, to be honest I have not shot it at 100 yards? Hope this will help you out.
Robert