josebd,
What are you using in the gun? If copper clad bullets, then you should be using a copper solvent and watching the patches coming out for blue-green color. If patches are being used with a brass brush or patch holder then you will see this telltale color because of the brass. Switch to an aluminum or plastic patch holder and then you'll know what the bore condition is truely like.
If you still can't get the patch to come out clean after repeated patching, then consider building an inexpensive electronic bore cleaning rod using a steel rod, a couple "C" batteries and some wire and clips. The solution is household ammonia. The plans are available on-line if you do a search on Google.
Jim