I'm with mete on this one.I used to build plastic injection molds.One of the ways to machine the cavity of the mold is with Electrical Discharge Machining.This process melts and recasts a thin skin of rough,imperfect steel that must be removed before polishing the cavity.While I often used stones in my reciprocating profile machine,I also did a lot of work with laps.I might use a small piece of cast iron or brass or copper for a lap.Diamond compound,or aluminum oxide or silicon carbide compounds were applied to the lap.The important thing to know,the grit embeds,sticks to,the softer metal.It is then like a file tooth that cuts the harder metal.You would be amazed how fast I could cut the recast EDM finish off the cavity with diamond compound and a lap.
You may rest assured as your bullets were bumping each other in your tumbler,you were embedding grit in the copper.I would not count on washing it all off.
Tell you what,try this.Take a piece of polished steel scrap,cold blue it,then rub one of your "clean" bullets on it ten strokes or so.(Or you could just grab some old Colt Python or a color case hardened Ballard or something and try it on the finish of fine gun,if you are very confident there is no grit..no,don't,I'm being a smart alec)
IMO,you have made fire lapping rounds.I would advise against shooting them.