I modified this expander from NOE to use with 9mm with cast bullets. I was running a batch and got the expander out and it has brass stuck to it, I can feel a ridge with my fingernail. How should I remove it without changing the size of the expander?

ETA... forgot the pic. Attached File

I was planning on trying the Dremel polishing wheel that I polished the expander with. At first it was sticking and making a lot of brass powdery mess. Polishing seemed to fix that.

Do you wet tumble your brass?

Use some Sweets 7.62 or KG-12 bore cleaner like Dryflash said.

Start by soaking with a saturated cleaning patch wrapped on there, then wait about 10 minutes and give it a spin with firm pressure.

Reapply that a few times before escalating to using the bore cleaner with ScotchBrite. You may clean up with just the cotton patch.

You would have to be very aggressive with abrasives to get a significant size change with your fingers and just cleaning.

You should take a magnified look before you start it up again. If the finish is too rough, you may want to polish it in the longitudinal direction to eliminate roughness and asperities that aide in galling.

Start up with brass that has been Dry Tumbled only and not US cleaned or wet tumbled to see if the tool picks up brass again. I would even do the first ones with some Imperial Die Wax on them just to see how it starts up. If this breaks in well, then see if the brass that did this galling will run next.

Sometimes brass that is cleaned aggressively is ready to react by galling.

I cleaned the brass in an ultrasonic cleaner with Lemi-shine.

I have som Sweets, I’ll give that a try.

I will inspect closely and polish the expander more.

Thanks for the tips.

I thought I had some corn cob but I can’t find it. I do have a vibratory tumbler. Anything else I could use? Cat litter? Silicone spray lube? Liquid lanolin? I want to load up some more ammo for Saturday, I do a 2x4 shoot once a month.

Can you exspander fit in a hand drill, lathe or drill press?.
Spin it and lightly use 2000- 2500 grit paper

You can get this at your NAPA store, car  painters  use it to remove scratches on clear coat

Steel wool