I use liquid M-Pro 7 in a spray bottle and really like it for removing carbon fouling. The gel version sounds interesting but I haven't tried it yet. Does it get rid of copper any better than the liquid?
A little off topic, but what the heck:
Just recently (6 months or so) I discovered my new favorite way for removing copper fouling. It's called "Wipe-Out Brushless Bore Cleaner." It's a foaming type cleaner, doesn't do much for carbon (despite the hype on the side of the can), but is fantastic for copper. I'll do my normal cleaning to get the carbon fouling out, then if I can see copper in the bore I'll spray this stuff down the barrel, leave it sit overnight so it's got plenty of time to work, then in the morning push a dry patch through the barrel and watch the stream of pretty blue fluid drain out (doing this over a trash can is highly recommended!) Even better, it lacks that lovely
ammonia aroma of so many other copper removers.