Update from the OP.
My bottle of M-Pro 7 gun cleaner arrived today from Amazon. As a test, I used it to clean my Glock semi-auto and my S&W revolver. I had already cleaned both guns -- CLP on the Glock and Ballistol on the S&W. I wanted to see how much more carbon the M-Pro 7 would remove from my already "clean" guns.
The results were positive. The M-Pro 7 removed quite a bit of leftover carbon from my Glock. Not so much from my S&W. I would say that M-Pro 7 is a much better cleaner than CLP and slightly better than Ballistol.
However, M-Pro 7 did not remove the dark smudges on the frame of my S&W. They are merely cosmetic, so that is not a big deal, but I can't give M-Pro 7 five stars for that reason.
After cleaning, I applied Rig liquid on metal parts for lubrication and protection. My guns are in much better shape than previously.
I should add that using a separate cleaner instead of an all-in-one product is the better way to go. It was always a pain removing excess CLP or Ballistol. The excess M-Pro 7 was quick and easy to remove.
I might try some of the other suggested products in the future, especially the lead away mentioned by cw308 for the carbon rings on the revolver.
Cheers.