I am attempting to polish my target action (receiver, baffle, recoil lug, trigger guard, bolt handle, etc.) with a maroon scotch brite pad finish. The bolt handle, trigger gurard, and baffle don't seem to be taking this finish. Are these cast parts? I have a SSS tactical bolt handle coming but assume this is cast as well? Any pointers on how to best polish them to match the receiver without having to put a mirror polish on everything?

Thank you,
Matt