Thanks-

I've put a lot of work into this rifle, it was in very rough shape when I got it. Working up to a load that gets the barrel groups together has been a tender tip-toe through the unknown. I just don't know anyone else running a BPE 450 double with these chambers. Marrakai's Tolley is similarly wacky, but his takes a bit less powder to do it's thing and I've been sweating it a bit on the way to converging groups -- his Tolley is quite a bit lighter than my rifle too.

Hopefully some time soon the weather will clear up some and I'll have time to get out to further run this load to see how it works out over the single express sight at 100 yards and beyond.
In don't want to press things much further as far as velocity goes although there's a 3-1/4" 500-450 BPE NFB in Wright's book that tested out at 2020fps and nine tons. He used Varget and this Hornady bullet. I think he used six fewer grains of powder to do it, but my chambers hold a lot more powder than the typical 3-1/4" case.
Nine tons pressure (compared to eleven tons pressure with original black powder ammunition pressures with 365gr nickel jacket bullets) with the smaller chambers of the 3-1/2" case gives me a bit of room to breath easy with this load and velocity in my much bigger chambers. I crept up to this load and there weren't any big or strange velocity steps along the way. All that and it has a good 'feel'

--Tinker