JB paste is for removing fouling. It isn't hard enough to do anything to your barrel. It will do a good job of cleaning though. If you want it to polish metal, there are too many other things that work better. JB won't actually remove metal, your mop or rag, steel wool, etc. will do a better job by itself (nothing on it).
I use it in my Bench rest rifle. It is the only thing I use that looks like a paste and may effect that hand lapped inside. Liquid, patches, and nylon bristle brushes are the only other thing that gets near the inside of that $500 barrel!
If it is cool outside, stick it out in the sun. The black top heats up quickly and turns it back into a useable paste. It also tends to seperate, stir it up if it hasn't been used in awhile.
Good stuff for cleaning.
Chris
