I know this is not AR, but its just plain "gun technical" and didn't know where to put it. Sorry if you need to move it.

I have an 870PM and it has light surface rust in the chamber... i did the usual 0000 Steel Wool wrapped around a patched brush and used my chamber cleaning tool to spin away and nada, nothing removed... any recommendations? Feeling like a noob, but I've always cleaned rust off with 0000 Steel Wool and WD40 with no problem... I used PB Blaster this time if that makes a difference. Thanks!

I have Flitz... should maybe I try that?