Acetic acid (vinegar) + Hydrogen Peroxide = peracetic acid (PAA)
Will dissolve or pit lead, copper, aluminum and uncoated carbon steels among other things. When it does, it forms metal-acetates… chiefly among concern is lead-acetate and cupric-acetate.
Leaded organic compound greatly increases lead’s bioavailability and even to the extent that it will be absorbed through skin. Cupric acetate is nasty too. Wear gloves and goggles. Once used to dissolve stuff like lead and copper it’s nasty hazmat… don’t dump this down the toilet or in the garden (dispose of properly).
Who cares about getting a FH mount “perfectly” clean anyways? It’s going to look fouled again after one mag. Scrape the caked shit and loose fouling off and carry on.