How to fix this die?

[Jackal2016]

I've had that happen from sizing new brass to ensure the case mouths were round. Basically just the brass galling inside the die. I removed it with Flitz or Autosol polish on a piece blue Scott towel wrapped around a bore brush and polished it out with a drill.

 

[Fire Dog]

I don't think Scotchbrite pads have an aggressive abrasive. I hand clean silverware with ScotchBrite all the time. It doesn't even scratch silverware. Wet grade sandpaper definitly works.

The colour of the pad indicates the coarseness of the Scotchbrite pad…
Even a green one is abrasive enough to scratch glass and the purple ones we {the SS handrail company I welded for} used that grade to restore the “Brushed” finished look on SS tubing… They are definitely coarse!
They make it right down to the equivalent of 000 steel wool… Wood workers now use this product for fine finish so that there is no iron left to rust a finished product.
I would advise when using a Scotchbrite pad or wet & dry fine sand paper to also wet them with bore cleaner as others have suggested and particularly if that is a copper specific product.. Have used the pads + Boretec Cu+2 to clean mandrels that had brass deposits and now use a wipe of Neolube#2 inside the neck and no more deposits…
Better case lubing, Imperial Die Wax or Ballistic Case Wax should eliminate the deposit from the outside of the case neck and wipes off with a twist on a paper towel.
Clean brass is also a must, does not need to be tumbled but at least think a hot water wash + a dash of dish soap… Then dry out on a tray in the oven 150*F and then start your reloading… Have seen dies from several friends ruined due to having sized dirty {from the ground or bench} brass and having grit particles score the steel of the die.

 

[Dgd6mm]

How is the die looking uncle buck?

 

[uncle-buck]

I tried several potential solutions without success and am going to send the die to Forster to be polished.

Am glad to have discovered the Iosso paste and oil. They are excellent products.

Thanks for all the replies and suggestions.

 

[LVLAaron]

3000 grit sandpaper. Like jackie said, it's hardened, you wont hurt it. The brass will buzz right off with some paper.