Just as a counterpoint, Squirrel has a good argument for use of filler. And I normally use COW. However, I always grease the chamber mouths, not to prevent chain fires, but so there is lube sliding down the bore before the ball and fouling contact the bore. I have shot over 100 shots in an afternoon with my ROA, and no cleaning necessary or binding up encountered during the whole afternoon.
Crisco is messy. Now a plea for help. For years I have been using Pistol Patch, a grease from Blue and Gray Products intended for cap and ball guns. I am on my last two tubes of the stuff. It comes in plastic tubes like tub caulk, and it is about the same consistency as fresh squeezed out caulk, except it never gets hard and doesn't dry out. I found one supplier and the price is quite high. Anybody know what the stuff really is? I'm sure Blue and Gray just bought large drums of the stuff and re-packaged it. BTW, I highly recommend the stuff, just not at $7.00 dollars a half pint.
Incidentally when I first started, the recommended grease to use was the special grease sold for repacking automobile water pumps.