There was a thread here before on this according to Google, but now it seems to be gone.
What's a recommended cleaner for the outside of a revolver, to get the carbon residue off?
My wife has a Ruger Security Six, and after cleaning the bore,  not really thinking I used a light amount of Hoppes 9 on a clean pad to then clean the gunk off the outside of the barrel and around the cylinder, and while I'm reasonably certain it's not a terrible thing to do (I immediately wiped it off and applied a light amount of lube and then wiped it down some more) especially considering it's a stainless steel finish, in hindsight it struck me as maybe not the smartest thing to make a habit of.  What is the best course of action for cleaning the outside of a gun like that?

Hopes #9 won't hurt quality stainless.  Especially if you wipe it right off like you did.

But it absolutely will DESTROY nickel plating of it stays on the nickel for an extended period.  Use sparingly on nickel plated guns.

Thanks.  
I did read that about nickel finishes, though I don't have anything with a nickel finish. The only other pistol I have that isn't a classic black semiauto is my PPK/S, which is also stainless.

It wront hurt it.
I have a Colt Gunsite 1911 it has a textured stainless finish.
It would get pretty sooted up towards the front of the slide.
I would use Bore solvant on it.
One day I spilled alittle Breakfree CLP on it and it actually cleaned it better.

So put alittle on a tooth brush and scrub, then walk away for 10 or 15 minuets .
Whats left should wipe off.

Never had an problem with either.  Had a nickel Beretta. I didn't soak the guns either.

Right.  You can use it on nickel but don't leave it on there.   Wipe it off just as soon as your done using it.  

No commercially available bore solvent will harm stainless steel unless you drop it into a tank full a super strong type and let it soak a few weeks.

Another good method of removing carbon and leading from STAINLESS STEEL is to buy a "lead-away" cloth.
These are a stiff yellowish cloth that literally wipes leading and carbon right off.
You can buy them in many gun stores and from Brownell's and Midway.

NOTE AND WARNING......... they will also literally wipe gun bluing right off, so NEVER use on a blued gun, and I wouldn't use it on a nickel gun either.

As for Hoppe's #9, you can leave it on carbon or stainless gun indefinitely and it will do no harm.
In the old days a lot of gun owners left Hoppe's #9 in the bore year around to protect from rust.

Not one of my stainless S&W revolvers (some old, some new) have ever been hurt by Hoppe's #9 which is all they have ever seen. That includes polished, bead blasted and satin.

The only danger with Hoppes 9 is with Nickle Plated firearms. The issue isn't with nickle plated itself but how it is put into your firearm. It doesn't bond with steal so what they do is put a thin layer of copper under it so it can bond with the firearm. It's perfectly safe to use it on nickle plate but the problem is sometimes there might be imperfections or chips on the surface that goes into the copper beneath. So the hoppes 9 is a copper solvent and leaving it in there or the liquid going into the cracks into the under surface copper area will be bad.

Other than that, you can leave it on pretty much any firearm out there for any period of time. Just don't leave it on plastic or something like that.

In my personal opinion, if you have reservations about it, maybe get something else like a bottle of Flitz or Iosso instead. It is the best at removing baked on carbon or copper and it won't damage your finish. Just use a small amount to test as it may rub off certain finishes.