"My lighter, longer-range load which basically duplicates a hot .45-70: 350 grain Hornady RNSP at 2280 fps."

That is a hot load for a 45-70!

I took my bison with my 1886 .45-90 using left over DG loads; 450 grain Kodiak FMJ with flat nose at 2150 fps. It shot clean through both shoulders and was over-kill, but I was my first bison so I used ammo that I knew would be effective.

BTW, Very nice looking double rifle.