I've read some fabulous, too-good-to-be-true statements about Gunslick Foaming Bore Cleaner.
One of these was that after one uses a conventional cleaner like Hoppe's #9, you can fill the bore with the foam and it'll take gunk out of what you thought was a clean barrel.
I figure the Mosin-Nagant M44 carbine I bought about a month ago is the perfect candidate for a test. I cleaned it a few days ago after shooting with LOTS of Hoppe's #9, followed by Outter's oil. It's not been shot since, and before I owned it I think it was likely last cleaned somewhere in the USSR in the 1940s.
It's soaking for 1/2 hour right now. After it's done I'm going to run dry patches through it. If I get green or brown, I'll treat it again. If I get clean, I'll follow up with a shot of G96 down the barrel.
I'll report back after I've cleaned it all the way.