If they are OK with having to re-touch the piece from time to time - BBQ Paint, or Rattle Can Krylon will work. Gun Solvents will remove these finishes quickly in my experince.

I have had great success with Alumahyde II from Brownell's, and even better success when used of a Home Parkerize Job - I got the Park kit from Shootersolutions.com It resists about any cleaning agent you would want to use on a Fire Arm, and adheres very well.

I have a Beater pump I need to refinish soon myself.

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