I shoot only real BP in my 45 Colt Remmie 1875's. The Remington does not handle BP very well and will require some special attention. Cleaning the gun with Ballistol and water works fine as does Windex Multi-Surface w/vinegar but I found that Ballistol alone will not keep my 1875's running for more than a stage or two when using Goex 2f and a 200gr Big Lube JP45.
I have to grease the pin, cylinder pin bore, and frame around the firing pin (head space) to get 6 stages without disassembling them.
I use the red Mobil One synthetic grease and it has been the only lube that keeps the 1875's with their tiny gas bushing running.
Willy