Yes the fouling.Bower64
I assume you are referring to powder fouling of the cylinder pin (arbor). I liberally apply lube to that area and clean/relube the pin When swapping cylinders. Periodically I remove the pin, dip in melted beeswax, let it harden, and repeat a couple times. I reinstall the cylinder and seat the pin. Any dry excess beeswax that gets removed When the pin is inserted seems to help in preventing effects of fouling of the pin in that área.
This is the only brass frame Remington 1858 ive ever shot and its the only one that when i shot it the cylinder would always lock up solid after every shot.
I tried pyrodex P and RS, T7 3F and T7 2F i think i even shot black MZ from it and every time the cylinder would lock up solid.
Ide have to move it back and forth while trying to rotate it and move the hammer then it would eventually free up for my next shot.
Only thing i could figure was the brass was pitted around the cylinder pin where it comes threw under the barrel. It didnt matter if i used ballistol, or antiseaze grease nothing helped it from locking up.