Yep, that JB Bore Compound or Iosso Bore Cleaner really slick up the bore of a new gun. I use it on all my new guns, blackpowder and smokeless.
It saves you a lot of ammunition, over the older practice of shooting lots of ammo to smooth the bore.
I've often wondered if a conical bullet, with its grease grooves, couldn't be filled with the above pastes and fired in a black powder revolver to smooth the bore too?
This would simply be a variation of the practice called "fire lapping."
But this would require far more compound than a tight patch worked back and forth and I'm rather stingy. Also, it may not work as well since the surface area of a patch is greater than any bullet.
Smoothing with a patch works, so I'm of the bent that if it isn't broke, don't fix it.
About once a year I use the same compounds to really clean the bores of my cap and ball revolvers. It's amazing how much lead it removes, lead you can't even see!
This unseen lead doesn't seem to affect accuracy but it gives me peace of mind. This is a job I do in the winter, when the snow is blowing horizontally and the wind is moaning like a Banshee.