This only costs pennies
Try scraping the rust spots with the edge of a copper coin. Be sure to use a coin that is real copper, not copper-washed steel (check with magnet).
The coin should be hard enough to remove the rust, but not the remaining bluing.
Finally, apply Hoppe's or similar, to remove the remaining rust AND the smears of copper left by the coin!
Stan
Try scraping the rust spots with the edge of a copper coin. Be sure to use a coin that is real copper, not copper-washed steel (check with magnet).
The coin should be hard enough to remove the rust, but not the remaining bluing.
Finally, apply Hoppe's or similar, to remove the remaining rust AND the smears of copper left by the coin!
Stan