I think the problem with a lot of these cleaners is...
First, real "Carbon" is not soluble in anything, and cannot be dissolved in anything. That's a basic chemical fact!
Second, the black crap is only partly Carbon - it's mostly ash that is composed of primer residue, some carbon, and unburnt/condensed nitrocellulose vapor and other transitional nitrogen chain compounds, and there are probably dozens of them.
Most of these things are only soluble in solvents based on petroleum based solvents like Kerosene, Benzene, Nitro-Benzene, Toluene, etc.
Based on what's in the cleaners now,and what the Gubbament has taken out of our real barrel cleaners in the last ten years)...
... I'm not so sure that it CAN be removed with any of the current "Magical Jooces"... I think it gets down to old fashioned elbow grease.
I keep hearing folks tout some new stuff, but when it's tried, it falls off the radar screen after a year or two... and then a new one pops up.
There is such a lucrative market for bore cleaners,they cost about 50 cents a gallon to make) that it's like making "Herbal medicines"... everyone keeps hoping for a new miracle, and every Tom, Dick and Harry keeps dreaming up a new brand of snake oil every 6 months :, :, :,
... and we keep praying.
.