All I can say is that hasn't been my experience. In my experience, even soaking a barrel in Kroil for days/weeks doesn't make it significantly easier/faster to clean than if I simply start out with a decent nitro solvent.
What I think is happening is that people find that they start getting clean patches faster when they use Kroil and that makes them think that Kroil is cleaning faster. What's really happening is that Kroil just isn't nearly as good at getting stuff out of the bore so the patches start coming out clean much faster.
Try this test.
Clean a barrel using
only Kroil and another one using
only a typical bore cleaner like Hoppes.
When you're done and believe the barrels are clean, wet each bore with BreakFree CLP, let it set for half an hour or so and then push another patch down the barrels. Save the patches. Then patch out the bores until they're completely dry and wet the bores with a dedicated copper solvent like Hoppes Benchrest #9. Wait however long the copper solvent instructions state and push dry patches down each barrel. Save those patches.
Now compare the patches and you can see whether Kroil or the bore cleaner works best. The cleaner which provides the cleanest patches did the best job.
...the kroil cleans, the jb polishes...
Ok, another issue here. If you're mixing Kroil and JB, then that's an entirely different issue. JB is an abrasive bore cleaner and, in my experience, abrasive bore cleaners are VERY effective at removing all types of bore fouling and are generally very fast. The only issue is that they are more aggressive than some people like.
If you're using a mixture of Kroil and JB, you will get the bore very clean very fast. However, in my experience, you'll get it just as clean, just as fast using only the JB.
