Use to get the brass or copper wool local Now its mail order . Ive used it like a patch but now in a pinch i use steel in the barrel. (Gta, steel wool patch thtead)
For pitted parts or complex shapes, the electrolysis process works wonders. Fortunately I haven’t needed it for gun projects but I processed a bunch of parts for a vintage table saw (Delta Unisaw) with it a while back and it worked beautifully.
A quick search turned up a video by Project Farm that serves as a good tutorial.
Well . Looking successful for cheap household vinegar. I dug them pliers up replacing crosstie corner / gate posts so every bit many years in the ground ( now if i could dig up the pocket knives i lost ).
Anyway start and today with only a few strokes of wire brush ( maybe 4-8 hits per side?)