Get some Kroil (preferred) or CLP Breakfree of a good penetrating fluid.
Liberally soak the rusty areas with the fluid and soak at least 24 hours. This will loosen and soften the rust.
After 24 hours, apply more fluid, then use a brass "toothbrush" to vigorously brush the rusty areas.
For heavier, crusty rust, make a scraper from sheet brass or by smashing the mouth of a BRASS rifle case shut, and filing it to a sharp chisel shape.
Use it to scrape the heavy rust.
After the rust is of, wipe the metal clean, and apply a coat of CLP Breakfree. This will continue to "work" on any rust, and will prevent more rust.
The brass brush trick will not damage the remaining blue like using even fine steel wool does. Also, don't use a penny or nickel.
They are no longer copper or nickel and will damage the blue.
Other advice for the Lawman:
If you dry fire it, use snap caps.
The Colt "J" frame firing pins "can" break if dry fired, and replacement is a factory ONLY job.
Replacement requires a special press with special shaped support dies and contour punches to press the old pin out and the new one in.
Using a hammer and punch WILL damage the frame.
Well if it cleans up with a rag and solvent than you have no further to go. Bt if the rust is to the point of pitting than a bitmore is called for. 0000 is the lightest steel wool made and is less abrasive than most brass brushes in my experience.Try it some time. A fella would have to do a lot of rubbing for it to harm any blueing much.
I had some reall good stuff that took all the rust off without leaving a tyrace but they don't make it any more. The closest I have found to that is Blue Wonder paste. it reomoves the rust really well and leaves not a mark at all. I have a Metropolitan MKIII 38 special only which is identical except for cylinder length (made 1969 to 1972 only) and many of these were once issued by NYPD along with the newer model of Official Police MKIII and had a good reputation. I bought mine used just as new in 1978-79. The big factory grips need replacing for anythin but single action target shooting IMHO. My brother has one made 1984 that is still working really well after countless rounds.
I have seen a LOT of these MKIIIs throw badly keyholed rounds on the range with lead bullets. Some really sheeted up badly with lead too. A Lewis Lead Remover works wonders on those models that do that. It is something to do with the .346 bore diameter cut into those Colt barrels. These guns do much better with jacketed bullets.
The hammer trigger et al are made of powdered metal so let's don't start that MIM thing but with a lot of officers I know carrying these a few ears ago I never heard of one breaking a part and mine run s just fine after about 28-29 years of moderate use since I got it. You have a very good gun there.
I just got this old girl off auction for a tad less the 300 shipped. Lawman MKIII. Doesn't appear to have been fired much. Excellent overall, EXCEPT for a nickel size pitted spot on the cylinder from apparently being holstered and unattended. Buffed and cold blued makes it a good carry/shooter. I also put a pair of Pachs on it. Debating about sending her off for a round butt job and bobbing the barrel to 3 inches. Refinish it off with something that wears well and looks like the old Coltguard finish. Suggestions???
Excellent! I would think that a finish that may help cover/protect the pitted area would be nice. There are so many more finishes out there than there used to e but hard chrome comes to mind.
I don't know if shortening the bbl 1" or so would be worth it to me. JMHO. I am 6' 4"-5" and can carry longer guns than some folks can. I wonder how well really hard cast SWCs would work in that tight barrel? I had a Python with those grips too. They have nice lines but just flare out to much for most people I swapped them out and ended up with Pachmayrs cause Hogues didn't work for me on a Colt as well as a S&W.
I always liked the S&W trigger over the Colt design and seemed tp shoot a little more equally bad with the Colts. The cylinder locking notches in that model are more offset away from the center of the chambers m akin it, at least in theory, stronger with hot loads; that was a major advertising point 30 years ago for Colts. It doesn't have the complex had of the Python
I bought a used Colt Lawman MKlll about a year and a half ago. It almost looked mint, but it had a severe carry over problem so I took it back to the dealer. It too had a two inch barrel and looked like the big brother to my 3rd generation Detective Special. I'm still keeping an eye out for another in great condition,