I make my scope cover out of duct tape. Underclocked gave me the measurements. I made up some in all colors of tape, and they work great. As for the rings, wipe them from time to time as you shoot and they will not be too bad at clean up.

All the open breech loader rifles are terrible when it comes to fouling. My Black Diamond, Staghorn, Wolverine, and all my Whites are open breech. I personally put up with the mess of the simplicity and smooth function of the rifle.

The duct tape scope covers are easy to clean, cheap to make, and work great.