Uberti brass vs. steel triggerguards

[Cimarron Lawman]

Update: Wet (oil) sanding the brass with 320 grit emery paper, followed by 600 grit, worked well.

[Flint]

I use 600 wet-or-dry to polish brass before buffing, I would never expect to clean up casting marks with it.  Starting with files, then 220, 320, 400 and 600.

Steel depends on the brand, polishing a Ruger is similar to trying to polish granite.  Gun bronze is harder than free machining brass by a bit, but it's softer than any of the steels even the Italians use, but bronze does not cut as easily as steel with an abrasive as the material behaves differently than steel.

For difficult machining, try copper.