I haven't had my AR-15 very long, and a few hundred rounds has already left a significant amount of brass residue on the case deflector. I don't think I want to take a bronze brush to it, for fear of taking off the finish. How does one go about removing that?

Regular gun cleaner, such as Hoppes, and some scrubbing with a hard plastic toothbrush should remove it. To keep it from happening again, take a small square of velcro (the cloth part, not the plastic part) and glue it onto the brass deflector. This will keep brass from accumulating on the deflector, and it keeps your brass from getting dented.

rt