I've wanted a 45-90 in an 1886 for quite a while, but have been too cheap to put up the coin, since 1886 45-90's go for a lot of money. I have a Miroku "1 in 500" 1886 in 45-70 that's pretty (and heavy) that I'd consider as a partial trade.
With the right bullets you can load and cycle 45/70 cartridges loaded to 45/90 length in your 1886 in 45/70. I can in my Browning 1886 in 45/70. This gives you the best of both options. 45/90 performance potential using 45/70 brass.
You need bore riding cast designs with a longish nose that have a crimp groove in the right place or, alternatively, use a Lee FCD to crimp in place.
